smtp.codes is a collection of SMTP response codes returned by email servers and a guide to help you understand what the SMTP codes that various email servers respond with mean.
4 |
5 |
This is super useful when troubleshooting email delivery and a tool every email marketer, deliverability person or email engineer should have in their tool kit. We welcome all contributions!
smtp.codes is a collection of SMTP response codes returned by email servers and a guide to help you understand what the SMTP codes that various email servers respond with mean.
4 |
5 |
This is super useful when troubleshooting email delivery and a tool every email marketer, deliverability person or email engineer should have in their tool kit. We welcome all contributions!
--------------------------------------------------------------------------------
/data/codes/422.json:
--------------------------------------------------------------------------------
1 | {
2 | "code": 422,
3 | "description": "The mail server encountered a temporary failure. If the command is repeated without any change, it might be completed. Mail servers can use temporary failures like this to keep untrusted senders at bay.",
4 | "providers": [
5 | {
6 | "id": "barracuda",
7 | "name": "Barracuda",
8 | "responses": [
9 | {
10 | "response": "422 License Expired",
11 | "description": "The recipient's Barracuda license expired and they are not processing any more emails.",
12 | "links": []
13 | }
14 | ]
15 | }
16 | ]
17 | }
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/data/codes/521.json:
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1 | {
2 | "code": 521,
3 | "description": "The transaction failed permanently. The server will not try to send the message again.",
4 | "providers": [
5 | {
6 | "id": "laposte",
7 | "name": "La Poste",
8 | "responses": [
9 | {
10 | "response": "521 5.7.1 Service unavailable LPN007_102",
11 | "description": "La Poste has blocked your IP for being in a blacklist. This code is usually associated with poor Validiy Sender Score reputation. Use the link below to check your Sender Score reputation and request a review.",
12 | "links": [
13 | "https:\/\/www.wombatmail.com\/dns.cgi?t=ptr"
14 | ]
15 | }
16 | ]
17 | }
18 | ]
19 | }
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/.github/workflows/build.yml:
--------------------------------------------------------------------------------
1 | name: Build and Deploy
2 |
3 | on:
4 | push:
5 | branches:
6 | - main
7 |
8 | jobs:
9 | build:
10 | runs-on: ubuntu-latest
11 |
12 | steps:
13 | - name: Checkout code
14 | uses: actions/checkout@v4
15 |
16 | - name: Set up PHP
17 | uses: shivammathur/setup-php@v2
18 | with:
19 | php-version: '8.3'
20 |
21 | - name: Run build script
22 | run: php build/build.php
23 |
24 | - name: Commit and push output
25 | run: |
26 | git config user.name "GitHub Actions"
27 | git config user.email "actions@github.com"
28 | git add docs/
29 | git commit -m "Update static site content" || echo "No changes to commit"
30 | git push
31 | env:
32 | GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
33 |
34 |
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/data/codes/540.json:
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1 | {
2 | "code": 540,
3 | "description": "The transaction failed permanently. The server will not try to send the message again. The email was returned to you likely because the intended recipient's account has been suspended or deactivated.",
4 | "providers": [
5 | {
6 | "id": "rambler",
7 | "name": "Rambler",
8 | "responses": [
9 | {
10 | "response": "540 5.7.1 : recipient address rejected: Inactive",
11 | "description": "",
12 | "links": []
13 | },
14 | {
15 | "response": "540 5.7.1 : recipient address rejected: Blocked",
16 | "description": "",
17 | "links": []
18 | }
19 | ]
20 | }
21 | ]
22 | }
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/data/contributors.json:
--------------------------------------------------------------------------------
1 | [
2 | {
3 | "name": "Anna Ward",
4 | "url": "https://resend.com/blog/welcoming-anna-ward"
5 | },
6 | {
7 | "name": "Derek Rushforth",
8 | "url": "https://derekrushforth.com"
9 | },
10 | {
11 | "name": "Chris Nagele",
12 | "url": "https://www.wildbit.com"
13 | },
14 | {
15 | "name": "Ashley Harpp",
16 | "url": ""
17 | },
18 | {
19 | "name": "Nicolò Rebughini",
20 | "url": ""
21 | },
22 | {
23 | "name": "Jan-Philipp Benecke",
24 | "url": "https://bnck.me/en/"
25 | },
26 | {
27 | "name": "Brian Kerr",
28 | "url": "https://briankerr.co"
29 | },
30 | {
31 | "name": "Shelley Jeżewska",
32 | "url": ""
33 | },
34 | {
35 | "name": "Faisal Misle",
36 | "url": "https://faisal.fm"
37 | },
38 | {
39 | "name": "Al Iverson",
40 | "url": "https://www.spamresource.com"
41 | },
42 | {
43 | "name": "Matt Heffelfinger",
44 | "url": "https://spamuraiwarrior.com"
45 | },
46 | {
47 | "name": "Yannic Röcken",
48 | "url": "https://indeno.at"
49 | }
50 | ]
51 |
--------------------------------------------------------------------------------
/LICENSE:
--------------------------------------------------------------------------------
1 | MIT License
2 |
3 | Copyright (c) 2025 Neatnik LLC & Faisal Misle
4 |
5 | Permission is hereby granted, free of charge, to any person obtaining a copy
6 | of this software and associated documentation files (the "Software"), to deal
7 | in the Software without restriction, including without limitation the rights
8 | to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
9 | copies of the Software, and to permit persons to whom the Software is
10 | furnished to do so, subject to the following conditions:
11 |
12 | The above copyright notice and this permission notice shall be included in all
13 | copies or substantial portions of the Software.
14 |
15 | THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 | IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 | FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
18 | AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 | LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
20 | OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
21 | SOFTWARE.
22 |
--------------------------------------------------------------------------------
/CONTRIBUTING.md:
--------------------------------------------------------------------------------
1 | ## Contribute
2 |
3 | Ran into an SMTP code that wasn't very helpful and you figured out what it means? or maybe you work for an email provicer and want to contribute the codes your service returns so you can decrease your support volume? We'd love to help you document them!
4 |
5 | If you plan on making additions or edits to existing SMTP responses, you’ll need to fork the repo and [submit a pull request](https://help.github.com/en/articles/creating-a-pull-request). All of the data is stored as JSON in the [/data](https://github.com/fm/smtp-codes/tree/main/data) folder. There's no need to set up the development environment for changes like this.
6 |
7 | If the provider doesn't exist, add it to `providers.json` first. Also, feel free to add yourself to `contributors.json` to show up in the Contributors page!
8 |
9 | Feel free to [file an issue](https://github.com/fm/smtp-codes/issues/new) if you don’t feel like dealing with code. If you do not have a GitHub account, you can also submit them via email at [submit@smtp.codes](mailto:submit@smtp.codes?subject=New%20code%20submission&body=Full%20SMTP%20response%3A%0AEmail%20provider%2Fserver%20returning%20the%20code%3A%0AAny%20other%20details%3A)
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/docs/540/index.html:
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5 | SMTP Error Code 540
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SMTP Error Code 540
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The transaction failed permanently. The server will not try to send the message again. The email was returned to you likely because the intended recipient's account has been suspended or deactivated.
The mail server encountered a temporary failure. If the command is repeated without any change, it might be completed. Mail servers can use temporary failures like this to keep untrusted senders at bay.
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/README.md:
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1 | # Welcome to smtp.codes
2 |
3 | We created this guide to help you understand what the SMTP codes that various email servers respond with. This is super useful when troubleshooting email delivery and a tool every email marketer, deliverability person or email engineer should have in their tool kit.
4 |
5 | ## Contribute
6 |
7 | Ran into an SMTP code that wasn't very helpful and you figured out what it means? or maybe you work for an email provicer and want to contribute the codes your services returns so you can decrease your support volume? We'd love to help you document them!
8 |
9 | If you plan on making additions or edits to existing SMTP responses, you’ll need to fork the repo and [submit a pull request](https://help.github.com/en/articles/creating-a-pull-request). All of the data is stored as JSON in the [/data](https://github.com/fm/smtp-codes/tree/main/data) folder. We recommend you run your changes through a [JSON linter](https://jsonlint.com) before commiting.
10 |
11 | Feel free to [file an issue](https://github.com/fm/smtp-codes/issues/new) if you don’t feel like dealing with code. If you do not have a GitHub account, you can also submit them via email at [submit@smtp.codes](mailto:submit@smtp.codes?subject=New%20code%20submission&body=Full%20SMTP%20response%3A%0AEmail%20provider%2Fserver%20returning%20the%20code%3A%0AAny%20other%20details%3A)
12 |
13 | ## Deployment
14 | A homegrown build script builds the website via an Action and then publishes it to GitHub Pages.
15 |
16 | ## Issues & Comments
17 | Feel free to contact us if you encounter any issues. Please leave all comments, bugs, requests and issues on the Issues page. If you do not have a GitHub account, you are welcome to send your feedback via email to [feedback@smtp.codes](mailto:feedback@smtp.codes)
18 |
19 | ## License
20 | smtp.codes is licensed under the MIT license. Please refer to the [LICENSE](https://github.com/fm/smtp-codes/blob/main/LICENSE) for more information.
21 |
22 | ## Acknowledgements
23 | We'd like to thank the ActiveCampaign Postmark team for spear-heading the initiative with SMTP Field Manual, from where we based the initial scope for this project.
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/docs/521/index.html:
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1 |
2 |
3 |
4 |
5 | SMTP Error Code 521
6 |
7 |
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SMTP Error Code 521
27 |
The transaction failed permanently. The server will not try to send the message again.
La Poste has blocked your IP for being in a blacklist. This code is usually associated with poor Validiy Sender Score reputation. Use the link below to check your Sender Score reputation and request a review.
550 5.7.1 Rejected by spam filter (in reply to end of DATA command)
Your email scored above the spam threshold and was rejected. Revise your email for any unwanted content prior to resending.
34 |
550 5.1.1 Recipient address rejected: Address does not exist
The email address does not exist. Check to make sure there are no typos or other mistakes with the address.
35 |
36 |
37 |
38 |
39 |
40 |
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47 |
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/data/codes/551.json:
--------------------------------------------------------------------------------
1 | {
2 | "code": 551,
3 | "description": "The transaction failed permanently. The server will not try to send the message again.",
4 | "providers": [
5 | {
6 | "id": "improvmx",
7 | "name": "ImprovMX",
8 | "responses": [
9 | {
10 | "response": "551 5.7.1 Due to the very low reputation of the sending domain, this message has been blocked (Code 2).",
11 | "description": "Your domain is on a reputation blacklist such as the Spamhaus DBL. You will need to be delisted before you can send emails.",
12 | "links": []
13 | },
14 | {
15 | "response": "551 5.7.1 Loop detected: Email is sent and forwarded from\/to improvmx.com. (#id-5.9.0)",
16 | "description": "The destination mailbox loops back to ImprovMX. They block these messages in order to avoid loops.",
17 | "links": []
18 | },
19 | {
20 | "response": "551 5.7.1 Domain not found (#id-5.9.2)",
21 | "description": "The domain was not found in the ImprovMX database.",
22 | "links": []
23 | },
24 | {
25 | "response": "551 5.7.1 Our database returned invalid pieces of information about the requested recipient\u2019s domain (#id-5.9.3)",
26 | "description": "",
27 | "links": []
28 | },
29 | {
30 | "response": "551 5.7.1 Unable to correctly read the forwarding recipient (where to forward the email to) (#id-5.9.5)",
31 | "description": "",
32 | "links": []
33 | }
34 | ]
35 | },
36 | {
37 | "id": "yandex",
38 | "name": "Yandex",
39 | "responses": [
40 | {
41 | "response": "551 5.3.0 Unknown error",
42 | "description": "",
43 | "links": []
44 | }
45 | ]
46 | }
47 | ]
48 | }
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/docs/amazonses/index.html:
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1 |
2 |
3 |
4 |
5 | Amazon Simple Email Service
6 |
7 |
8 |
9 |
10 |
11 |
12 |
13 |
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15 |
16 |
17 |
18 |
19 |
20 |
21 |
22 |
23 |
24 |
25 |
26 |
Amazon Simple Email Service
27 |
Amazon Simple Email Service (also known as "Amazon SES") is an email platform used for inbound and outbound email sending as a part of Amazon Web Services (AWS). It is also used as a MTA backend for Amazon WorkMail, their email hosting product. Typically the recipient themselves will need to open a ticket with AWS support for in-depth troubleshooting if the issue can't be resolved using manual controls.
HEY is an email provider offered by the software company 37Signals. It's a paid service for both hey.com recipients and those with their own domain hosting email in the HEY app. HEY boasts especially strict spam filtering and a manual screening process per sender. There's little a sender can do to troubleshoot delivery, as the individual recipient decides which email addresses they accept mail from.
FireEye is a spam filter, block list, and firewall solution for businesses. Mail is routed through mailservers owned by FireEye before it's passed along to the recipient domain's mailservers for final delivery. The recipient is able to manage a lot of delivery settings such a allow lists, so it helps to ask the recipient to run the described debugging tests in the user guide to identify and resolve delivery issues.
550 5.7.26 <example@example.com>: ETP205 DMARC Failure for domain
The email failed DMARC and you have a reject policy. Make sure your email is authenticated and aligned with SPF and/or DKIM. Contact your email provider for more details on how to configure them.
Cisco Secure Email is a spam filter, block list, and firewall solution for businesses. Mail is routed through mailservers owned by Cisco (iphmx.com) before it's passed along to the recipient domain's mailservers for final delivery. The recipient is able to manage a lot of delivery settings such a allow lists,so it helps to ask the recipient to run the described debugging tests in the user guide to identify and resolve delivery issues, as there is no way to contact the vendor directly.
550 5.7.1 Your access to submit messages to this e-mail system has been rejected.
This occurs when there is a block on something on the message; either your IP or domain have low reputation as reported by Cisco's Threat Intelligence or a manually set policy. You may want to contact the recipent through alternate ways so they can check the logs and add you to an allow list or contact Talos for a reclassification.
T-Online is the email service of Deutsche Telekom, one of Germany's largest telecommunications providers. It offers both free and paid email accounts, featuring webmail access, POP3/IMAP support, spam and virus protection, and integration with Telekom's MagentaCloud storage.
550 5.7.0 Message considered as spam or virus, rejected
Your message has been rejected due to spam or virus classification. If you believe this is incorrect, please report the above error codes to FPR@RX.T-ONLINE.DE so we can investigate the classification. We apologize for any inconvenience and thank you for your support.
ZeroSpam is a spam filter, block list, and firewall promoted for businesses, headquartered in Quebec. Mail is routed through mailservers owned by ZeroSpam before it's passed along to the recipient domain's mailservers for final delivery. The recipient is able to manage a lot of delivery settings such as allow lists, but senders may also be able to contact a postmaster@zerospam.com and abuse@zerospam.com address to get more in-depth analysis.
450 4.2.0 <email@example.com>: Recipient address rejected: example.com greylisted for 60 seconds by ZEROSPAM
Greylisting is a common antispam measure. This mesage is asking the sending mail server to retry sending, most mail servers handle this automatically and will resend the message automatically, leading to a successful delivery.
MXroute is an email host obsessed with high IP reputation. They offer a low-cost, no-frills solution that guarantees delivery of your corporate emails.
550 Unauthenticated mail not allowed from this range
The sending IP is in a range of IPs that are considered low reputation or should not be sending emails. If you believe this to be a false positive, request a review at https://whitelistrequest.mxrouting.net
34 |
550 No such recipient here
The email address does not exist. Check to make sure there are no typos or other mistakes with the address.
550-SPF-check failed: 550 example.com doesn't allow sending mails from xx.xx.xx.xx (in reply to MAIL FROM command)
The sent message failed the SPF policy for the sending domain. To resolve this, you'll need to make sure the mail server you are sending mail from is in the sending domain's SPF record.
38 |
550 Message from example.com failed sender's DMARC policy, REJECT
The sent message failed the DMARC policy for the sending domain. If the sending domain has a reject policy set for DMARC, the message must pass DKIM or have SPF aligned to the domain with a custom Return-Path. To resolve this, you'll need to contact your email service provider to see how to configure SPF and/or DKIM properly.
39 |
550 no such address here
The email address does not exist. Check to make sure there are no typos or other mistakes with the address.
40 |
550 no such address here (MX do not point to us)
The domain was not found in their system, or was not added correctly, so they can't route emails.
Rambler is a search engine and email provider, headquartered in Moscow. Besides a general contact form available in their support resources pages, you can also reach out to Rambler's abuse team directly at abuse@rambler-co.ru to investigate false-positive blocks.
450 4.1.8 Sender address rejected: Domain not found (in reply to RCPT TO command))
The sender domain is not a valid domain or the domain has not been registered yet. This prevents spammers from making up non-existent domains that can't receive email.
550 5.7.1 rejected by DMARC policy for example.com (in reply to end of DATA command),
The email failed DMARC and you have a reject policy. Make sure your email is authenticated and aligned with SPF and/or DKIM. Contact your email provider for more details on how to configure them.
42 |
550 5.1.1 Recipient address rejected: User unknown in virtual mailbox table,
The email address does not exist. Check to make sure there are no typos or other mistakes with the address
You are sending an email to a server that has not been configured to receive email for that domain.
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/data/codes/501.json:
--------------------------------------------------------------------------------
1 | {
2 | "code": 501,
3 | "description": "The transaction failed permanently. The server will not try to send the message again. This is most commonly an issue with an incorrect\/invalid email address.",
4 | "providers": [
5 | {
6 | "id": "outlook",
7 | "name": "Outlook.com",
8 | "responses": [
9 | {
10 | "response": "501 5.1.3 Invalid address [outlook.com]",
11 | "description": "",
12 | "links": []
13 | }
14 | ]
15 | },
16 | {
17 | "id": "yahoo",
18 | "name": "Yahoo",
19 | "responses": [
20 | {
21 | "response": "501 Syntax error in parameters or arguments",
22 | "description": "",
23 | "links": [
24 | "https:\/\/postmaster.yahooinc.com\/error-codes"
25 | ]
26 | }
27 | ]
28 | },
29 | {
30 | "id": "gmx",
31 | "name": "GMX",
32 | "responses": [
33 | {
34 | "response": "501 Syntax error in parameters or arguments",
35 | "description": "Due to an incorrect configuration, email reception has been refused. Please contact your administrator who should correct the server configuration based on our recommendations and apply to us for the systems to be unblocked.",
36 | "links": [
37 | "https:\/\/postmaster.gmx.net\/en\/error-messages"
38 | ]
39 | }
40 | ]
41 | },
42 | {
43 | "id": "qq",
44 | "name": "QQ",
45 | "responses": [
46 | {
47 | "response": "501 Bad address syntax. http:\/\/service.exmail.qq.com\/cgi-bin\/help?subtype=1&&id=20022&&no=1000730",
48 | "description": "",
49 | "links": [
50 | "http:\/\/service.exmail.qq.com\/cgi-bin\/help?subtype=1&&id=20022&&no=1000730"
51 | ]
52 | }
53 | ]
54 | },
55 | {
56 | "id": "orange",
57 | "name": "Orange",
58 | "responses": [
59 | {
60 | "response": "501 5.1.0 Emetteur invalide. Invalid Sender. OFR004_405 [405]",
61 | "description": "This error suggests that Orange is seeing an issue with the Return-Path (SPF) of the message. Check the settings with your sending email provider to make sure your Return-Path is aligned with your sending domain.",
62 | "links": []
63 | }
64 | ]
65 | },
66 | {
67 | "id": "godaddy",
68 | "name": "GoDaddy",
69 | "responses": [
70 | {
71 | "response": "HELO\/EHLO rejected. IB301",
72 | "description": "The server is rejecting the HELO\/EHLO command. Try using a different HELO\/EHLO string, and verify the one you are using isn't being abused.",
73 | "links": []
74 | }
75 | ]
76 | }
77 | ]
78 | }
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/docs/mailru/index.html:
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1 |
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4 |
5 | Mail.ru
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Mail.ru
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Mail.ru is an internet service provider and email provider, headquartered in Moscow. They have strict published requirements for delivering mail, such as prohibiting the use of link shorteners. All senders should register their sending domains for Mail.ru's Postmaster Tools for direct insight into reputation and performance in the inbox.
550 Message was not accepted -- invalid mailbox. Local mailbox example@mail.ru is unavailable: account is disabled
44 |
550 spam message rejected. Please visit http://help.mail.ru/notspam-support/id?c=7y4ytdHbuOGv3O50NYTwpz1F-TVIpnactxtFPeFQSDYMAAAAaKgAAOX_3hE~ or report details to abuse@corp.mail.ru. Error code: ###. ID: #
While a message being rejected as spam isn't good news for anyone, this bounce response is especially helpful for those who don't typically send to Russian domains. In those cases, you'll see this bounce when online forms are being exploited by spam bots repeatedly victimizing Mail.ru recipients. Please check all of your online forms to be sure that they are properly protected.
AT&T offers free email accounts for past customers at sbcglobal.net and bellsouth.net, and new and non-customers can register an att.net or currently.com free email account. AT&T provides a detailed Postmaster page with contact options for investigating false-positive spam verdicts.
550 5.7.1 Connections not accepted from servers without a valid sender domain. ## Fix reverse DNS for x.xx.xx.xx
Usually this is a reverse DNS (PTR) issue with the sending IP, but sometimes lookup failures by AT&T can cause this bounce to be a false-positive. After confirming reverse DNS is properly set up and the record has fully propagated, try resending the message.
smtp.codes is a collection of SMTP response codes returned by email servers and a guide to help you understand what the SMTP codes that various email servers respond with mean.
29 |
30 |
This is super useful when troubleshooting email delivery and a tool every email marketer, deliverability person or email engineer should have in their tool kit. We welcome all contributions!
La Poste is a public-owned French postal company that also provides @laposte.net addresses to French residents. They have strict SPF, DKIM & DMARC requirements to reduce the amount of spam, similar to Gmail and Yahoo.
La Poste has blocked your IP for being in a blacklist. This code is usually associated with poor Validiy Sender Score reputation. Use the link below to check your Sender Score reputation and request a review.
550 5.7.1 Suspicion de contenu non sollicite. Afin de preserver la qualite du service et limiter les volumes de spam sur la plateforme, ce message n'a pas ete transmis. Likely unsolicited email. LPN007_510
La Poste has determined your messages are unsolicited, so your message was rejected. Contact their team to get more details about the reason behind the block.
550 5.7.20 Message refuse, DKIM n'est pas configure sur votre domaine d'expedition. Message refused, DKIM is not configured on your sending domain. LPN007_402
The message does not have a DKIM signature, or, none of the DKIM signatures is aligned with the domain in the RFC5322.From header. Contact your email provider to setup DKIM correctly with a signature on your domain.
Orange is an internet service provider that provides free email accounts to both its customers and registered non-customers, headquartered in France. Eurproean receivers tend to have high expectations for GDPR legal complaince, so after you've ensured the mail is legitimate and following all best practices, you can typically report false-positive blocks and spam filtering to Orange's "Abuse Cell" team to investigate.
This error suggests that Orange is seeing an issue with the Return-Path (SPF) of the message. Check the settings with your sending email provider to make sure your Return-Path is aligned with your sending domain.
550 5.2.0 Mail rejete. Mail rejected. ofr_506 [506]
42 |
550 5.1.1 Adresse d au moins un destinataire invalide. Invalid recipient. OFR_416 [416]
You have sent to a mailbox that doesn't exist. Make sure there are no typos or other errors.
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550 mwinfXXXX ME Adresse IP source bloquee pour incident de spam. Client host blocked for spamming issues. OFR006_102 Ref http://csi.cloudmark.com/reset-request/?ip=xxx.xxx.xxx.xxx [102]
Your IP has been blocked by Cloudmark Sender Intelligence and must be delisted to deliver mail.
"Email Security.cloud" is a product working in combination with "Symantec Messaging Gateway" as part of a range of services offered by Broadcom. It features spam filtering, firewall protection, and block lists. Mail is routed through mailservers owned by them (messagelabs.com) before it's passed along to the recipient domain's mailservers for final delivery. The recipient is able to manage a lot of delivery settings such a allow lists, so it helps to ask the recipient to run the described debugging tests in the user guide to identify and resolve delivery issues, as there is no way to contact the vendor directly.
450 Requested action aborted [9] #-#, please visit https://knowledge.broadcom.com/external/article?legacyId=TECH246726 for more details about this error message.
Your message triggered a spam rule. Contact the mail admin via alternate means so they can check the logs and troubleshoot.
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553 you are trying to use me [xx.messagelabs.com] as a relay, but I have not been configured to let you [x.xx.xx.xx, example.com] do this. (#5.7.1)
You are delivering mail to a domain not configured to use their service. There is little you can do, as it's likely a misconfiguration on the receiver's end.
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/data/codes/553.json:
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1 | {
2 | "code": 553,
3 | "description": "The transaction failed permanently. The server will not try to send the message again. ",
4 | "providers": [
5 | {
6 | "id": "google",
7 | "name": "Google",
8 | "responses": [
9 | {
10 | "response": "553 5.1.2 The recipient address is not a valid RFC-5321 address. - gsmtp",
11 | "description": "The recipient address is malformed. Please verify and try again.",
12 | "links": [
13 | "https:\/\/tools.ietf.org\/html\/rfc5321"
14 | ]
15 | }
16 | ]
17 | },
18 | {
19 | "id": "zoho",
20 | "name": "Zoho",
21 | "responses": [
22 | {
23 | "response": "failed,5.1.1 (bad destination mailbox address),553 Relaying disallowed,mx.zoho.com",
24 | "description": "",
25 | "links": []
26 | }
27 | ]
28 | },
29 | {
30 | "id": "yahoo",
31 | "name": "Yahoo",
32 | "responses": [
33 | {
34 | "response": "host xx.yahoodns.net [x.xx.xx.xx] SMTP error from remote mail server after MAIL FROM: SIZE=2022: 553 5.7.1 [BL21] Connections will not be accepted from x.xx.xx.xx, because the ip is in Spamhaus's list; see http:\/\/postmaster.yahoo.com\/550-bl23.html",
35 | "description": "Your IP is listed in the Spamhaus ZEN list. Spamhaus is a very reputable block list with few false-positive listings. Use the link below to check the status of your IP. You must cooperate with Spamhaus to resolve the listing. Remember that even once the listing is removed, it may take receivers up to 24 hours to refresh their cache and to see delivery resume.",
36 | "links": [
37 | "https:\/\/check.spamhaus.org",
38 | "https:\/\/postmaster.yahooinc.com\/error-codes"
39 | ]
40 | },
41 | {
42 | "response": "host xx.yahoodns.net [x.xx.xx.xx] SMTP error from remote mail server after MAIL FROM: SIZE=2022: 553 Mail from x.xx.xx.xx not allowed - 5.7.1 [BL23] Connections not accepted from IP addresses on Spamhaus XBL [550]",
43 | "description": "Your IP is listed in the Spamhaus XBL list. Spamhaus is a very reputable block list with few false-positive listings. Use the link below to check the status of your IP. You must cooperate with Spamhaus to resolve the listing. Remember that even once the listing is removed, it may take receivers up to 24 hours to refresh their cache and to see delivery resume.",
44 | "links": [
45 | "https:\/\/check.spamhaus.org",
46 | "https:\/\/postmaster.yahooinc.com\/error-codes"
47 | ]
48 | }
49 | ]
50 | },
51 | {
52 | "id": "emailsecuritycloud",
53 | "name": "Email Security.cloud",
54 | "responses": [
55 | {
56 | "response": "553 Message filtered. (#5.7.1)",
57 | "description": "Your message triggered a spam rule. Contact the mail admin via alternate means so they can check the logs and troubleshoot.",
58 | "links": []
59 | },
60 | {
61 | "response": "553 you are trying to use me [xx.messagelabs.com] as a relay, but I have not been configured to let you [x.xx.xx.xx, example.com] do this. (#5.7.1)",
62 | "description": "You are delivering mail to a domain not configured to use their service. There is little you can do, as it's likely a misconfiguration on the receiver's end.",
63 | "links": []
64 | }
65 | ]
66 | }
67 | ]
68 | }
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/docs/501/index.html:
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SMTP Error Code 501
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The transaction failed permanently. The server will not try to send the message again. This is most commonly an issue with an incorrect/invalid email address.
Due to an incorrect configuration, email reception has been refused. Please contact your administrator who should correct the server configuration based on our recommendations and apply to us for the systems to be unblocked.
This error suggests that Orange is seeing an issue with the Return-Path (SPF) of the message. Check the settings with your sending email provider to make sure your Return-Path is aligned with your sending domain.
Free is an internet service provider headquartered in France. It provides free email accounts to its customers, notably those of Free and Alice. Their postmaster page is filled with detailed information about error codes and IP lookup options, including instructions to report a false-positive spam verdict.
Free.fr determined the message that you sent included spam content. Check your mail to make sure it should not be missdetected as a spam, either by using an antispam softwate or by checking if the mail is syntaxically correct.
550 5.2.1 This mailbox has been blocked due to inactivity
The mailbox is not currently active because of inactivity from the recipient. Once the recipient reactivates their mailbox, they'll be able to receive messages again.
Free.fr has detected a virus in the message that you sent. Check your mail to make sure it should not be missdetected as a spam, either by using an antispam softwate or by checking if the mail is syntaxically correct.
GMX is an email provider including Mail.com recipients, headquartered in Germany. European receivers tend to have high expectations for GDPR legal complaince, and in some cases email deliverability is aided when the sender is included in high profile "whitelists" and certification programs. You can use the GMX postmaster site to investigate most issues, and their contact form to submit things for in-depth investigation. You can also reach out to mailsecurity@gmxnet.de directly in urgent cases.
Due to an incorrect configuration, email reception has been refused. Please contact your administrator who should correct the server configuration based on our recommendations and apply to us for the systems to be unblocked.
550 Requested action not taken: mailbox unavailable
The specified recipient does not exist on their systems or the recipient has not used their inbox for an extended period of time and the inbox has been temporarily disabled due to inactivity. Please check the spelling of the email address.
Requested action not taken: mailbox unavailable Reject due to policy restrictions.
The message is being rejected due to policy reasons. This is likely down to the sender or IP being a spam source, or technical information included in the email doesn't meet some RFC standards.
552 Requested mail action aborted: exceeded storage allocation Quota exceeded.
We were unable to deliver your email because the potential recipient does not have sufficient free space in their inbox. Please use a different method to contact the person in question and inform them of the situation.
Trend Micro is a spam filter, block list, and firewall solution for businesses. Mail is routed through mailservers owned by Trend Micro (example: *.trendmicro.com). The recipient is able to manage a lot of delivery settings such a allow lists, so it helps to ask the recipient to run the described debugging tests in the user guide to identify and resolve delivery issues.
'ERS' stands for Trend Micro's 'Email Reputation System', which provides custom levels of threat protection including sensitivity preferences and custom filters.
There's certain criteria in the message itself that this recipient is blocking, which could include a block on the sender's domain/IP by an admin of the recipient's domain.
The recipient is permanently undeliverable unless manual changes are made on the recipient's end to allow the sender's domain and/or sending IP. This doesn't necessarily mean the message was purposefully blocked, just that routing of the message through Trend Micro is not yet allowed.
Your message triggered a spam rule. Contact the mail admin via alternate means so they can check the logs and troubleshoot.
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553 you are trying to use me [xx.messagelabs.com] as a relay, but I have not been configured to let you [x.xx.xx.xx, example.com] do this. (#5.7.1)
You are delivering mail to a domain not configured to use their service. There is little you can do, as it's likely a misconfiguration on the receiver's end.
host xx.yahoodns.net [x.xx.xx.xx] SMTP error from remote mail server after MAIL FROM:<user@example.com> SIZE=2022: 553 5.7.1 [BL21] Connections will not be accepted from x.xx.xx.xx, because the ip is in Spamhaus's list; see http://postmaster.yahoo.com/550-bl23.html
Your IP is listed in the Spamhaus ZEN list. Spamhaus is a very reputable block list with few false-positive listings. Use the link below to check the status of your IP. You must cooperate with Spamhaus to resolve the listing. Remember that even once the listing is removed, it may take receivers up to 24 hours to refresh their cache and to see delivery resume.
host xx.yahoodns.net [x.xx.xx.xx] SMTP error from remote mail server after MAIL FROM:<user@example.com> SIZE=2022: 553 Mail from x.xx.xx.xx not allowed - 5.7.1 [BL23] Connections not accepted from IP addresses on Spamhaus XBL [550]
Your IP is listed in the Spamhaus XBL list. Spamhaus is a very reputable block list with few false-positive listings. Use the link below to check the status of your IP. You must cooperate with Spamhaus to resolve the listing. Remember that even once the listing is removed, it may take receivers up to 24 hours to refresh their cache and to see delivery resume.
Zoho allows the receiving domain to set mail filters. The receiving domain has filters set-up that are blocking this message. To resolve this, you'll need to contact an administrator of this domain through another channel to have them adjust their filters and allow delivery.
452 <example@zoho.com> Mailbox delivery restricted by policy error
Zoho allows the receiving domain to set mail filters. The receiving domain has filters set-up that are blocking this message. To resolve this, you'll need to contact an administrator of this domain through another channel to have them adjust their filters and allow delivery.
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452 4.3.1 Temporary System Error
This indicates that the domain at Zoho is not currently accepting email. Sending messages again in the future will most likely be successful.
550 5.7.1 Email rejected per DMARC policy for example.com
The email failed DMARC and you have a reject policy. Make sure your email is authenticated and aligned with SPF and/or DKIM. Contact your email provider for more details on how to configure them.
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550 5.1.1 <example@zoho.com> User unknown
The email address does not exist. Check for typos or other errors.
A known virus was detected in your message content, attachments, and/or URLs. Run the full message and its headers through a virus scanner to identify the source.
QQ is an instant messaging service that includes email, social groups and games, and online chat products, headquartered in China as part of Tencent. Email delivery can be unpredicatable for non-Chinese businesses or when sending through mailservers outside of China. For the most insight, register your Return-Path domain with QQ's Postmaster site to directly monitor delivery and respond to any spam complaints.
The recipient you're trying to send to is receiving a large number of emails in a short period of time. To avoid malicious attacks, sending to this recipient is temporarily prohibited.
The sender 's sending frequency exceeded the limit. The amount of time that further mail is prohibited from being delivered depends on the limit exceeded. (for example, sender, hourly, daily). These limits are not disclosed.
The email failed DMARC and you have a reject policy. Make sure your email is authenticated and aligned with SPF and/or DKIM. Contact your email provider for more details on how to configure them.
Yandex is a search engine and email provider, headquartered in Moscow. They have strict published requirements for delivering mail, such as details on the opt-in and unsubscribe process. They used to maintain a detailed postmaster tools site, but it was discontinued due to abuse of the service.
554 5.7.1 [1] Message rejected under suspicion of SPAM; https://ya.cc/1IrBc ##
While a message being rejected as spam isn't good news for anyone, this bounce response is especially helpful for those who don't typically send to Russian domains. In those cases, you'll see this bounce when online forms are being exploited by spam bots repeatedly victimizing Yandex recipients. Please check all of your online forms to be sure that they are properly protected.
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/data/codes/452.json:
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1 | {
2 | "code": 452,
3 | "description": "The mail server encountered a temporary failure. If the command is repeated without any change, it might be completed. Mail servers can use temporary failures like this to keep untrusted senders at bay.",
4 | "providers": [
5 | {
6 | "id": "google",
7 | "name": "Google",
8 | "responses": [
9 | {
10 | "response": "452 4.2.2 The email account that you tried to reach is over quota. Please direct the recipient to https:\/\/support.google.com\/mail\/?p=OverQuotaTemp - gsmtp",
11 | "description": "Google Mail has has restrictions on the amount of storage a user can use, the recepiepnt is over their storage limit and unable to receive new messages. They will need to delete emails to start to receive messages again. Once they've done this, they'll be able to start to receive messages again.",
12 | "links": [
13 | "https:\/\/support.google.com\/mail\/answer\/6374270?p=OverQuotaTemp&visit_id=637466814024175068-236829835&rd=2"
14 | ]
15 | }
16 | ]
17 | },
18 | {
19 | "id": "yahoo",
20 | "name": "Yahoo",
21 | "responses": [
22 | {
23 | "response": "452 temporary domain failure ",
24 | "description": "The mail server encountered a temporary failure. Most likely it isn't anything to do with the session, but rather the server is overloaded or having issues. If you try again later, it should work.",
25 | "links": [
26 | "https:\/\/postmaster.yahooinc.com\/error-codes"
27 | ]
28 | }
29 | ]
30 | },
31 | {
32 | "id": "outlook",
33 | "name": "Outlook.com",
34 | "responses": [
35 | {
36 | "response": "452 4.3.1 Insufficient system resources (TSTE) [outlook.com]",
37 | "description": "The receiving mail server is currently out of storage space. The administers at the receiving domain will need to resolve this issue. Once they've done this, they'll be able to start to receive messages again.",
38 | "links": []
39 | }
40 | ]
41 | },
42 | {
43 | "id": "zoho",
44 | "name": "Zoho",
45 | "responses": [
46 | {
47 | "response": "452 Mailbox delivery restricted by policy error",
48 | "description": "Zoho allows the receiving domain to set mail filters. The receiving domain has filters set-up that are blocking this message. To resolve this, you'll need to contact an administrator of this domain through another channel to have them adjust their filters and allow delivery.",
49 | "links": []
50 | },
51 | {
52 | "response": "452 4.3.1 Temporary System Error",
53 | "description": "This indicates that the domain at Zoho is not currently accepting email. Sending messages again in the future will most likely be successful.",
54 | "links": []
55 | }
56 | ]
57 | },
58 | {
59 | "id": "comcast",
60 | "name": "Comcast",
61 | "responses": [
62 | {
63 | "response": "452 4.1.1 too many recent messages; Try again later",
64 | "description": "The email address is currently receiving an email at a high rate. Sending email in the future will most likely be successful.",
65 | "links": [
66 | "http:\/\/postmaster.comcast.net\/"
67 | ]
68 | },
69 | {
70 | "response": "452 4.1.1 user over quota",
71 | "description": "The email address is currently receiving an email at a high rate. Sending email in the future will most likely be successful.",
72 | "links": [
73 | "http:\/\/postmaster.comcast.net\/"
74 | ]
75 | }
76 | ]
77 | },
78 | {
79 | "id": "rambler",
80 | "name": "Rambler",
81 | "responses": [
82 | {
83 | "response": "452 4.5.3 rate limit exceeded",
84 | "description": "The email address is currently receiving an email at a high rate. Sending email in the future will most likely be successful.",
85 | "links": [
86 | "http:\/\/postmaster.comcast.net\/"
87 | ]
88 | }
89 | ]
90 | },
91 | {
92 | "id": "godaddy",
93 | "name": "GoDaddy",
94 | "responses": [
95 | {
96 | "response": "452 $(_toemail) temporarily unavailable. Try again later.",
97 | "description": "The mail server encountered a temporary failure. Most likely it isn't anything to do with the session, but rather the server is overloaded or having issues. If you try again later, it should work.",
98 | "links": []
99 | }
100 | ]
101 | }
102 | ]
103 | }
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Comcast (also known as "Xfinity") is an American internet service provider that also provides email addresses to its customers. Former customers can still have access to their comcast.net address if they've logged in in the past 90 days, but that also means many of these addresses become inactive over time.
550 5.2.0 Message rejected due to DMARC. Please see http://postmaster.comcast.net/smtp-error-codes.php#DM000001
The email failed DMARC and you have a reject policy. Make sure your email is authenticated and aligned with SPF and/or DKIM. Contact your email provider for more details on how to configure them.
host xx.comcast.net [x.xx.xx.xx] SMTP error from remote mail server after initial connection: 554 xx.comcast.net comcast x.xx.xx.xx Comcast requires that all mail servers must have a PTR record with a valid Reverse DNS entry. Currently your mail server does not fill that requirement. For more information, refer to: http://postmaster.comcast.net/smtp-error-codes.php#554
The mail server encountered a temporary failure. If the command is repeated without any change, it might be completed. Mail servers can use temporary failures like this to keep untrusted senders at bay.
452 $(_toemail) temporarily unavailable. Try again later.
The mail server encountered a temporary failure. Most likely it isn't anything to do with the session, but rather the server is overloaded or having issues. If you try again later, it should work.
452 4.2.2 The email account that you tried to reach is over quota. Please direct the recipient to https://support.google.com/mail/?p=OverQuotaTemp - gsmtp
Google Mail has has restrictions on the amount of storage a user can use, the recepiepnt is over their storage limit and unable to receive new messages. They will need to delete emails to start to receive messages again. Once they've done this, they'll be able to start to receive messages again.
452 4.3.1 Insufficient system resources (TSTE) [outlook.com]
The receiving mail server is currently out of storage space. The administers at the receiving domain will need to resolve this issue. Once they've done this, they'll be able to start to receive messages again.
The mail server encountered a temporary failure. Most likely it isn't anything to do with the session, but rather the server is overloaded or having issues. If you try again later, it should work.
452 <example@zoho.com> Mailbox delivery restricted by policy error
Zoho allows the receiving domain to set mail filters. The receiving domain has filters set-up that are blocking this message. To resolve this, you'll need to contact an administrator of this domain through another channel to have them adjust their filters and allow delivery.
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452 4.3.1 Temporary System Error
This indicates that the domain at Zoho is not currently accepting email. Sending messages again in the future will most likely be successful.
Web.de is a search engine and email provider, headquartered in Germany. Eurproean receivers tend to have high expectations for GDPR legal complaince, and in some cases email deliverability is aided when the sender is included in high profile "whitelists" and certification programs.
550 <example@example.com>: Reject due to SPF policy. The originating IP of the message is not permitted by the domain owner
The email was rejected, because it was sent from a server that is not included in the domain owner's SPF record. This usually indicates that the sender address has been spoofed and that the email is spam/phishing.
550 <example@example.com>: Syntax error in parameters or arguments
Due to an incorrect configuration, email reception has been refused. Please contact your administrator who should correct the server configuration based on their recommendations.
550 <example@example.com>: Requested action not taken: mailbox unavailable
The specified recipient does not exist on their systems or the recipient has not used their inbox for an extended period of time and the inbox has been temporarily disabled due to inactivity.
550 <example@example.com>: Bad DNS PTR resource record
Emails from your email server were rejected because the PTR Resource Record of your IP address does not follow their guidelines. Possible reasons for this can be: The PTR-RR states that the IP address was dynamically allocated or the PTR-RR is a generic standard entry of your provider. Please allocate an independent and fully qualified domain name to your email server.
550 <example@example.com>: Reject due to policy restrictions (header based)
Your message will be rejected by their system if: any of the technical information included in the email doesn't meet the standards, the email violates their guidelines or, it is not plausible, i.e.: when specifying the date. This is applicable to all emails with more than one of the following headers: BCC, CC, Date, From, Sender, Subject, To. In addition, the headers "Date, From, Sender, To" must be syntactically correct.
550 <example@example.com>: Reject due to policy restrictions (IP based)
If a high percentage of e-mails are classified as spam by their filters, all messages coming from the sender's IP address will be temporarily rejected for a specific time frame.
Barracuda is a spam filter, block list, and firewall for businesses. Mail is routed through mailservers owned by Barracuda before it's passed along to the recipient domain's mailservers for final delivery. The recipient is able to manage a lot of delivery settings such as allow lists, but sender reputation issues that affect all Barracuda customers globally may require contacting Barracuda support directly to resolve.
This response is followed by the bounce received from one of the intended recipients of the message. You'll want to resolve the delivery issue for the quoted recipient before sending to this group of addresses again.
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422 License Expired
The recepient domain uses a Barracuda mail filter and their license for that service is expired. They'll need to resolve their license issue with Barracuda to start to receive messages again.
If you know the recipient personally, try reaching out through other means to confirm why the message was rejected (include the full source and headers of the rejected message). Only the recipient and their mailserver admin can resolve this bounce.
550 cuda_nsu 5.1.1 <email@example.com> Recipient address rejected: User unknown
This mailbox does not exist at this mail server. Check to make sure there are no typos with the address.
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550 No such user (email@example.com)
This mailbox does not exist at this mail server. Check to make sure there are no typos with the address.
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550 Blocked
Barracuda states that a 550 SMTP code means that the requested command failed because the user's mailbox was unavailable (for example, because it was not found, or because the command was rejected for policy reasons).
Barracuda thinks you're attempting to impersonate a known brand. Check your sending domains, 'From' details, and content and links for potential unintended references.
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550 permanent failure for one or more recipients (email@example.com:blocked)
This specific message is being blocked for content or domain related reasons. It's not necessarily a permanent failure since a different message may deliver later.
A URL in your message content may be on a public or private block list. Some recipients may also filter URLs based on their geo-location. Check all of the domains, subdomains, and full URLs in your content against as many public lists as you can to narrow-down the culprit.
Check your content, phrasing, and links for any potentially suspicious characteristics. Even something as simple as an unfortunate typo or a link to an exploited webpage can block a message from delivering.
Exchange Online Protection (EOP) is the spam filter for Microsoft 365, the business productivity suite from Microsoft. It provides businesses with spam filtering, block lists, and firewall protection. If a message is going to spam or getting blocked, there are typically instructions for the email admin to fix the specific error in Exchange documentation.
421 4.3.2 The maximum number of concurrent connections per resource forest has exceeded a limit, closing transmission channel. example.com. PRX8 [example.com]
451 4.7.0 Temporary server error. Please try again later. PRX4 NextHop: example.com [example.com]
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451 4.7.500 Server busy. Please try again later from [x.xx.xx.x]. (AS77712344) [#.prod.protection.outlook.com]
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451 4.4.62 Mail sent to the wrong Office 365 region. ATTR35. For more information please go to https://go.microsoft.com/fwlink/?linkid=865268 [#.prod.protection.outlook.com]
This error can result from misconfigured connectors, expired certificates, or incorrect mail routing in hybrid Exchange environments.
Usually this bounce means the recipient address is invalid, but sometimes it can be caused by internal setup or routing issues. Reach out to the recipient's mail admin to verify.
550 5.7.1 Service unavailable, Client host [x.xx.xx.xx] blocked using Spamhaus. (AS16012611)
Exchange Online checks the sending IP against the public block list Spamhaus. Spamhaus is a very reputable block list with few false-positive listings. Use the link below to check the status of your IP. You must cooperate with Spamhaus to resolve the listing. Remember that even once the listing is removed, it may take receivers up to 24 hours to refresh their cache and to see delivery resume.
550 5.7.1 Service unavailable, Helo domain is listed in Spamhaus. (S8001) [#.prod.protection.outlook.com]
First, the forward DNS lookup (domain name to IP address) of your sending IP should match the HELO value set in your mailserver. Then Exchange Online checks this HELO domain against the public block list Spamhaus. Spamhaus is a very reputable block list with few false-positive listings. Use the link below to check the status of your IP. You must cooperate with Spamhaus to resolve the listing. Remember that even once the listing is removed, it may take receivers up to 24 hours to refresh their cache and to see delivery resume.
550 5.7.606 Access denied, banned sending IP [x.xx.xx.xx]. To request removal from this list please visit https://sender.office.com/ and follow the directions. For more information please go to http://go.microsoft.com/fwlink/?LinkID=526655 (AS16012609)
Your IP has low reputation with Microsoft. Follow the instructions on the link below to suubmit mitigation. You may need to reply to their emails a few times.
554 5.4.14 Hop count exceeded - possible mail loop ATTR34
That means the message is being passed around like a hot potato between servers. Possible reasons include: A misconfigured hybrid environment; internal M365 wonkiness; they are forwarding it somewhere, and it's being sent back to 365 multiple times; a mailbox is being migrated between clusters, or the mailbox was corrupted/misconfigured. There is nothing you as the sender can do; if it's an important email, try contacting the recipient via alternate means.
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/data/codes/552.json:
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1 | {
2 | "code": 552,
3 | "description": "The transaction failed permanently. The server will not try to send the message again. ",
4 | "providers": [
5 | {
6 | "id": "google",
7 | "name": "Google",
8 | "responses": [
9 | {
10 | "response": "552 5.2.2 The email account that you tried to reach is over quota. Please direct the recipient to https:\/\/support.google.com\/mail\/?p=OverQuotaPerm - gsmtp",
11 | "description": "",
12 | "links": [
13 | "https:\/\/support.google.com\/mail\/answer\/81126"
14 | ]
15 | },
16 | {
17 | "response": " 552-5.2.3 Your message exceeded Google's message size limits. Please visit http:\/\/mail.google.com\/support\/bin\/answer.py?answer=8770 to review our size guidelines.",
18 | "description": "",
19 | "links": [
20 | "http:\/\/mail.google.com\/support\/bin\/answer.py?answer=8770"
21 | ]
22 | },
23 | {
24 | "response": " 552-5.7.0 Our system detected an illegal attachment on your message. Please visit http:\/\/mail.google.com\/support\/bin\/answer.py?answer=6590 to review our attachment guidelines.",
25 | "description": "",
26 | "links": [
27 | "http:\/\/mail.google.com\/support\/bin\/answer.py?answer=6590"
28 | ]
29 | }
30 | ]
31 | },
32 | {
33 | "id": "zoho",
34 | "name": "Zoho",
35 | "responses": [
36 | {
37 | "response": "552 5.1.1 Mailbox delivery failure policy error",
38 | "description": "",
39 | "links": []
40 | },
41 | {
42 | "response": "552 5.7.1 virus [name] detected by Zoho Mail",
43 | "description": "A known virus was detected in your message content, attachments, and\/or URLs. Run the full message and its headers through a virus scanner to identify the source.",
44 | "links": []
45 | }
46 | ]
47 | },
48 | {
49 | "id": "yahoo",
50 | "name": "Yahoo",
51 | "responses": [
52 | {
53 | "response": "552 1 Requested mail action aborted, mailbox not found",
54 | "description": "Treat this bounce as a 'bad-mailbox'. Experience has shown that the email address is invalid and should not be sent to in the future.",
55 | "links": [
56 | "https:\/\/postmaster.yahooinc.com\/error-codes"
57 | ]
58 | }
59 | ]
60 | },
61 | {
62 | "id": "yandex",
63 | "name": "Yandex",
64 | "responses": [
65 | {
66 | "response": "552 5.2.2 Mailbox size limit exceeded",
67 | "description": "The recipient's mailbox is full. This usually happens because the recipient does not use their mailbox often and their mailbox is full.",
68 | "links": [
69 | "https:\/\/yandex.com\/support\/mail\/bounces\/yandex.html"
70 | ]
71 | }
72 | ]
73 | },
74 | {
75 | "id": "icloud",
76 | "name": "iCloud",
77 | "responses": [
78 | {
79 | "response": "552 5.2.2 : user is overquota",
80 | "description": "",
81 | "links": [
82 | "https:\/\/support.apple.com\/en-us\/HT204137"
83 | ]
84 | }
85 | ]
86 | },
87 | {
88 | "id": "orange",
89 | "name": "Orange",
90 | "responses": [
91 | {
92 | "response": "552 5.1.1 Boite du destinataire pleine. Recipient overquota. OFR_417 [417]",
93 | "description": "",
94 | "links": []
95 | }
96 | ]
97 | },
98 | {
99 | "id": "free",
100 | "name": "Free",
101 | "responses": [
102 | {
103 | "response": "552 5.2.2 user quota exceeded (UserSearch)",
104 | "description": "",
105 | "links": []
106 | }
107 | ]
108 | },
109 | {
110 | "id": "comcast",
111 | "name": "Comcast",
112 | "responses": [
113 | {
114 | "response": "552 5.1.1 recipient rejected - extended quota violation",
115 | "description": "",
116 | "links": [
117 | "http:\/\/postmaster.comcast.net\/"
118 | ]
119 | }
120 | ]
121 | },
122 | {
123 | "id": "gmx",
124 | "name": "GMX",
125 | "responses": [
126 | {
127 | "response": "552 Requested mail action aborted: exceeded storage allocation Quota exceeded.",
128 | "description": "We were unable to deliver your email because the potential recipient does not have sufficient free space in their inbox. Please use a different method to contact the person in question and inform them of the situation.",
129 | "links": [
130 | "https:\/\/postmaster.gmx.net\/en\/error-messages"
131 | ]
132 | }
133 | ]
134 | },
135 | {
136 | "id": "godaddy",
137 | "name": "GoDaddy",
138 | "responses": [
139 | {
140 | "response": "552 $(_sid) - $(_id) Message size exceeds maximum permitted. Please reduce message size, and retry.",
141 | "description": " The message size exceeds the maximum limit set by the recipient's email server. This can happen if the email contains large attachments or if the total size of the email exceeds the allowed limit (Currently 30MB).",
142 | "links": []
143 | },
144 | {
145 | "response": "552 $(_sid) - $(_id) Virus infected message rejected. IB705",
146 | "description": "A known virus was detected in your message content, attachments, and\/or URLs. Run the full message and its headers through a virus scanner to identify the source.",
147 | "links": [
148 | "https:\/\/www.secureserver.net\/help\/fix-rejected-email-with-a-bounce-error-40685?pl_id=3153&prog_id=3153#crb>"
149 | ]
150 | },
151 | {
152 | "response": "552 $(_sid) - $(_id) This message has been rejected due to content judged to be spam by the internet community IB212 - If you feel this is in error, please submit a request using the link below.",
153 | "description": "The message was rejected because it was detected as spam. This can happen if the email contains certain domains, keywords, ipaddresses, phrases, etc that are commonly associated with spam and have been reported as such.",
154 | "links": [
155 | "https:\/\/checkspam.secureserver.net\/?sid=$(_sid)&mid=$(_id"
156 | ]
157 | }
158 | ]
159 | }
160 | ]
161 | }
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/docs/552/index.html:
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5 | SMTP Error Code 552
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SMTP Error Code 552
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The transaction failed permanently. The server will not try to send the message again.
552 Requested mail action aborted: exceeded storage allocation Quota exceeded.
We were unable to deliver your email because the potential recipient does not have sufficient free space in their inbox. Please use a different method to contact the person in question and inform them of the situation.
552 $(_sid) - $(_id) Message size exceeds maximum permitted. Please reduce message size, and retry.
The message size exceeds the maximum limit set by the recipient's email server. This can happen if the email contains large attachments or if the total size of the email exceeds the allowed limit (Currently 30MB).
A known virus was detected in your message content, attachments, and/or URLs. Run the full message and its headers through a virus scanner to identify the source.
552 $(_sid) - $(_id) This message has been rejected due to content judged to be spam by the internet community IB212 - If you feel this is in error, please submit a request using the link below.
The message was rejected because it was detected as spam. This can happen if the email contains certain domains, keywords, ipaddresses, phrases, etc that are commonly associated with spam and have been reported as such.
552 5.2.2 The email account that you tried to reach is over quota. Please direct the recipient to https://support.google.com/mail/?p=OverQuotaPerm - gsmtp
552-5.7.0 Our system detected an illegal attachment on your message. Please visit http://mail.google.com/support/bin/answer.py?answer=6590 to review our attachment guidelines.
A known virus was detected in your message content, attachments, and/or URLs. Run the full message and its headers through a virus scanner to identify the source.
iCloud provides Apple customers with free email accounts. Users can also link their custom domains to it. Their postmaster includes some basic deliverability recommendations, but troubleshooting requires contacting their Postmaster team.
Messages are not being accepted right now. You may usually see this for sends happening at the "top of the hour" when many senders around the world are also sending aggressively to Apple.
550 5.7.1 [CS01] Message rejected due to local policy. Please visit https://support.apple.com/en-us/HT204137
Apple Mail is blocking the email because of an email filter policy on their end. If you're unsure of the source of this issue, and following Apple's suggested best practices, you can contact Apple's postmaster team with mail logs for delivery support.
550 5.7.1 Your message was rejected due to example.com DMARC policy.
The email failed DMARC and you have a reject policy. Make sure your email is authenticated and aligned with SPF and/or DKIM. Contact your email provider for more details on how to configure them.
550 5.7.1 Your email was rejected due to having a domain present in the Spamhaus DBL -- see https://www.spamhaus.org/dbl/
Apple Mail checks all URLs in your message content against the public block list Spamhaus. Spamhaus is a very reputable block list with few false-positive listings. Use the link below to check the status of your IP. You must cooperate with Spamhaus to resolve the listing. Remember that even once the listing is removed, it may take receivers up to 24 hours to refresh their cache and to see delivery resume.
554 5.7.1 [CS01] Message rejected due to local policy.
Apple Mail is blocking the email because of an email filter policy on their end. Usually due to to the sender domain / IP reputation. If you're following Apple's suggested best practices, you can also contact Apple's postmaster team with mail logs for delivery support.
554 5.7.1 [HM08] Message rejected due to local policy.
Apple Mail is blocking the email because of an email filter policy on their end. Usually due to to the sender domain / IP reputation. If you're following Apple's suggested best practices, you can also contact Apple's postmaster team with mail logs for delivery support.
554 5.7.1 [BS01] Message rejected due to local policy.
Apple Mail is blocking the email because of an email filter policy on their end. Please make sure that affected customers have valid SPF, DKIM and DMARC to remediate them. If you're following Apple's suggested best practices, you can also contact Apple's postmaster team with mail logs for delivery support.
Proofpoint is a spam filter for businesses. Mail is routed through mailservers owned by Proofpoint (*.pphosted.com or *.ppe-hosted.com) before it's passed along to the recipient domain's mailservers for final delivery. The recipient is able to manage a lot of delivery settings such a allow lists and spam filtering policy levels. For globally-blocked IPs, the adminstrator of the IP will need to request delisting directly.
421 4.1.1 <email@example.com>: Recipient address rejected: unverified address: host example.com[x.xx.xx.xx] said: 450 4.1.1 <email@example.com>: Recipient address rejected: unverified address: lost connection with mail.example.com[x.xx.xx.xx] while sending RCPT TO (in reply to RCPT TO command)
Mail is routed through mailservers owned by Proofpoint before it's passed along to the recipient domain's mailservers for final delivery. If the message is rejected when Proofpoint attempts to finally deliver the message, they'll quote this rejection within the bounce response they send back to you. This is an example of that kind of relayed/quoted bounce.
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550 5.1.1 User Unknown
The email address does not exist. Please check address for typos or other errors.
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550 5.1.1 - This is not a valid email address. Please verify that you have the correct email address for your recipient.
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550 5.1.8 <sender@example.com>: Sender address rejected: Domain not found (in reply to RCPT TO command)
Make sure your 'From' and 'Return-Path' (envelope-from used for SPF) domains exist can receive mail.
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550 5.1.8 Domain of sender address does not exist
Make sure your 'From' and 'Return-Path' (envelope-from used for SPF) domains exist can receive mail.
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550 5.5.2 <email@example.com>: Sender address rejected: need fully-qualified address (in reply to RCPT TO command)
Make sure your 'From' and 'Return-Path' (envelope-from used for SPF) domains exist can receive mail.
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550 5.7.0 Email rejected per sender's DMARC policy
The sent message failed the DMARC policy for the sending domain. If the sending domain has a reject policy set for DMARC, the message must pass DKIM or have SPF aligned to the domain with a custom Return-Path. To resolve this, you'll need to contact your email service provider to see how to send a message that passes DMARC.
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550 5.7.1 <email@example.com>: Recipient address rejected: User email address is marked as invalid.
The email address was marked as invalid by Proofpoint after being rejected by the recipient's mail server. If this is a valid address, the mail admin needs to remove it from the invalid list in the Proofpoint Admin Console.
550 5.7.1 Service unavailable; client [x.xx.xx.xx] blocked using Cloudmark Sender Intelligence (Visit http://csi.cloudmark.com/reset-request/ if you feel this is in error)
Your IP has been blocked by Cloudmark Sender Intelligence and must be delisted to deliver mail.
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/data/codes/450.json:
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1 | {
2 | "code": 450,
3 | "description": "The mail server encountered a temporary failure. If the command is repeated without any change, it might be completed. Mail servers can use temporary failures like this to keep untrusted senders at bay.",
4 | "providers": [
5 | {
6 | "id": "google",
7 | "name": "Google",
8 | "responses": [
9 | {
10 | "response": "450 4.2.1 The user you are trying to contact is receiving mail at a rate that prevents additional messages from being delivered. Please resend your message at a later time. If the user is able to receive mail at that time, your message will be delivered. For more information, please visit https:\/\/support.google.com\/mail\/?p=ReceivingRate - gsmtp",
11 | "description": "The email address is currently receiving an email at a high rate. Sending email in the future will most likely be successful.",
12 | "links": [
13 | "https:\/\/support.google.com\/mail\/answer\/81126"
14 | ]
15 | }
16 | ]
17 | },
18 | {
19 | "id": "yahoo",
20 | "name": "Yahoo",
21 | "responses": [
22 | {
23 | "response": "450 User is receiving mail too quickly",
24 | "description": "The email address is currently receiving an email at a high rate. Sending email in the future will most likely be successful.",
25 | "links": [
26 | "https:\/\/postmaster.yahooinc.com\/error-codes"
27 | ]
28 | }
29 | ]
30 | },
31 | {
32 | "id": "outlook",
33 | "name": "Outlook.com",
34 | "responses": [
35 | {
36 | "response": "450 4.7.3 Organization queue quota exceeded. [outlook.com]",
37 | "description": "The receiving email domain is currently receiving an email at a high rate. This messages indicates the domain is not currently able to receive emial. Sending email in the future will most likely be successful.",
38 | "links": []
39 | }
40 | ]
41 | },
42 | {
43 | "id": "yandex",
44 | "name": "Yandex",
45 | "responses": [
46 | {
47 | "response": "450 4.2.1 The recipient has exceeded message rate limit. Try again later.",
48 | "description": "The email address is currently receiving an email at a high rate. Sending email in the future will most likely be successful.",
49 | "links": []
50 | }
51 | ]
52 | },
53 | {
54 | "id": "infomaniak",
55 | "name": "Infomaniak",
56 | "responses": [
57 | {
58 | "response": "450 4.1.8 Sender address rejected: Domain not found (in reply to RCPT TO command))",
59 | "description": "The sender domain is not a valid domain or the domain has not been registered yet. This prevents spammers from making up non-existent domains that can't receive email.",
60 | "links": []
61 | }
62 | ]
63 | },
64 | {
65 | "id": "improvmx",
66 | "name": "ImprovMX",
67 | "responses": [
68 | {
69 | "response": "450 4.2.1 Please try again later. (#id-5.9.4)",
70 | "description": "Their anti-spam check failed. We need the sender to retry sending.",
71 | "links": []
72 | }
73 | ]
74 | },
75 | {
76 | "id": "comcast",
77 | "name": "Comcast",
78 | "responses": [
79 | {
80 | "response": "450 4.2.0 - Recipient temporarily unavailable",
81 | "description": "The email address is currently unable to receive email. Sending email in the future will most likely be successful.",
82 | "links": []
83 | }
84 | ]
85 | },
86 | {
87 | "id": "rackspace",
88 | "name": "Rackspace",
89 | "responses": [
90 | {
91 | "response": "450 4.7.1 Client host {IP} has no PTR record (G1F)",
92 | "description": "Rackspace require that incoming IPs have a valid PTR. If you run your own server, consult your IP provider on how to add it. Else contact your email provider's support team.",
93 | "links": [
94 | "https:\/\/postmaster.emailsrvr.com\/system-info\/response-codes"
95 | ]
96 | },
97 | {
98 | "response": "450 4.7.1 Client host {IP} has no PTR record (G1F)",
99 | "description": "Rackspace require that incoming IPs have a valid PTR. If you run your own server, consult your IP provider on how to add it. Else, contact your email provider's support team.",
100 | "links": [
101 | "https:\/\/postmaster.emailsrvr.com\/system-info\/response-codes"
102 | ]
103 | },
104 | {
105 | "response": "450 4.4.1 : The recipient's server was temporarily unavailable to accept your message (G6)",
106 | "description": "A temporary failure while attempting to verify the recipient address. Retrying in a few minutes should work.",
107 | "links": [
108 | "https:\/\/postmaster.emailsrvr.com\/system-info\/response-codes"
109 | ]
110 | },
111 | {
112 | "response": "450 4.2.1 : Mailbox received too much email in a short period of time (G30)",
113 | "description": "Rackspace rate limit inbound email to mailboxes to protect the entire system. The user may be experiencing a list bomb attack or similar and trying again in a few minutes should work.",
114 | "links": [
115 | "https:\/\/postmaster.emailsrvr.com\/system-info\/response-codes"
116 | ]
117 | },
118 | {
119 | "response": "450 4.4.6 Routing loop detected (G16)",
120 | "description": "An undeliverable mail loop was detected. Try again in a few minutes; if it does not subside, try contacting postmaster@emailsrvr.com",
121 | "links": [
122 | "https:\/\/postmaster.emailsrvr.com\/system-info\/response-codes"
123 | ]
124 | },
125 | {
126 | "response": "450 4.4.0 Temporary DMARC DNS lookup failure (G1E)",
127 | "description": "A temporary failure while looking up sender's DMARC policy. Trying again in a few minutes should succeed.",
128 | "links": [
129 | "https:\/\/postmaster.emailsrvr.com\/system-info\/response-codes"
130 | ]
131 | }
132 | ]
133 | },
134 | {
135 | "id": "barracuda",
136 | "name": "Barracuda",
137 | "responses": [
138 | {
139 | "response": "450 cuda_nsu 4.7.1 : Recipient address rejected: Policy Rejection- Abuse. Go away.",
140 | "description": "If you know the recipient personally, try reaching out through other means to confirm why the message was rejected (include the full source and headers of the rejected message). Only the recipient and their mailserver admin can resolve this bounce.",
141 | "links": []
142 | }
143 | ]
144 | },
145 | {
146 | "id": "emailsecuritycloud",
147 | "name": "Email Security.cloud",
148 | "responses": [
149 | {
150 | "response": "450 Requested action aborted [9] #-#, please visit https:\/\/knowledge.broadcom.com\/external\/article?legacyId=TECH246726 for more details about this error message.",
151 | "description": "",
152 | "links": []
153 | }
154 | ]
155 | },
156 | {
157 | "id": "zerospam",
158 | "name": "ZeroSpam",
159 | "responses": [
160 | {
161 | "response": "450 4.2.0 : Recipient address rejected: example.com greylisted for 60 seconds by ZEROSPAM",
162 | "description": "Greylisting is a common antispam measure. This mesage is asking the sending mail server to retry sending, most mail servers handle this automatically and will resend the message automatically, leading to a successful delivery.",
163 | "links": []
164 | }
165 | ]
166 | }
167 | ]
168 | }
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5 | SMTP Error Code 450
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SMTP Error Code 450
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The mail server encountered a temporary failure. If the command is repeated without any change, it might be completed. Mail servers can use temporary failures like this to keep untrusted senders at bay.
If you know the recipient personally, try reaching out through other means to confirm why the message was rejected (include the full source and headers of the rejected message). Only the recipient and their mailserver admin can resolve this bounce.
450 Requested action aborted [9] #-#, please visit https://knowledge.broadcom.com/external/article?legacyId=TECH246726 for more details about this error message.
450 4.2.1 The user you are trying to contact is receiving mail at a rate that prevents additional messages from being delivered. Please resend your message at a later time. If the user is able to receive mail at that time, your message will be delivered. For more information, please visit https://support.google.com/mail/?p=ReceivingRate - gsmtp
The email address is currently receiving an email at a high rate. Sending email in the future will most likely be successful.
450 4.1.8 Sender address rejected: Domain not found (in reply to RCPT TO command))
The sender domain is not a valid domain or the domain has not been registered yet. This prevents spammers from making up non-existent domains that can't receive email.
The receiving email domain is currently receiving an email at a high rate. This messages indicates the domain is not currently able to receive emial. Sending email in the future will most likely be successful.
450 4.7.1 Client host {IP} has no PTR record (G1F)
Rackspace require that incoming IPs have a valid PTR. If you run your own server, consult your IP provider on how to add it. Else contact your email provider's support team.
450 4.7.1 Client host {IP} has no PTR record (G1F)
Rackspace require that incoming IPs have a valid PTR. If you run your own server, consult your IP provider on how to add it. Else, contact your email provider's support team.
450 4.2.1 <email@example.com>: Mailbox received too much email in a short period of time (G30)
Rackspace rate limit inbound email to mailboxes to protect the entire system. The user may be experiencing a list bomb attack or similar and trying again in a few minutes should work.
450 4.2.0 <email@example.com>: Recipient address rejected: example.com greylisted for 60 seconds by ZEROSPAM
Greylisting is a common antispam measure. This mesage is asking the sending mail server to retry sending, most mail servers handle this automatically and will resend the message automatically, leading to a successful delivery.