Summary
The 550 5.4.1 'Recipient address rejected: Access denied AS(201806281)' bounce error in O365 accounts is multi-faceted. Causes range from third-party scanner interference and Mimecast relay issues to incorrect recipient addresses and domain configuration problems. Proofpoint being involved, spam blocking, invalid addresses, blacklisting, recipient server issues, inactive mailboxes, and email restrictions are all possible contributors. Troubleshooting involves verifying addresses, checking MX records, sender IP reputation, authentication settings, and mailbox status. Microsoft documentation highlights potential misconfigurations and the impact of Directory Based Edge Blocking (DBEB). The error signals a permanent delivery failure, necessitating thorough investigation of both sender and recipient environments.
Key findings
- Third-party Scanners: Third-party scanners integrated with online Exchange can reject emails.
- Mimecast Relay: Bounces can occur during Mimecast relaying to O365.
- Invalid Addresses: Incorrect or non-existent recipient addresses cause rejection.
- Domain Config Issues: Recipient domain misconfigurations and authentication problems lead to errors.
- DBEB Impact: Directory Based Edge Blocking (DBEB) rejects messages for invalid recipients.
- Spam Blocking: Emails might be blocked as spam, not just due to unknown user.
- Blacklisting: Sender's IP or domain could be blacklisted, causing rejection.
- Server Issues: Temporary recipient server problems can result in the error.
- Permanent Error: 5.4.1 code means the destination server refused to deliver the message.
- Proofpoint: Email could have been blocked by Proofpoint.
Key considerations
- Address Verification: Always verify the recipient's email address for accuracy.
- MX Record Check: Ensure MX records are correctly configured for the domain.
- Sender Reputation: Check sender IP and domain reputation for blacklisting.
- Authentication Settings: Review and correct domain authentication settings (SPF, DKIM, DMARC).
- Mailbox Status: Confirm that the recipient's mailbox is active and accepting emails.
- Third-party Scanners: Investigate potential interference from third-party email scanners and security services (e.g., Proofpoint, Mimecast).
- Retry Delivery: Retrying delivery at a later time could solve the issue due to temporary server issues.
- Contact Admin: Contact the recipients admin to ensure email can be delivered correctly.
What email marketers say
7 marketer opinions
The 550 5.4.1 bounce error in O365 accounts, indicated by 'Recipient address rejected: Access denied AS(201806281)', is caused by several factors. These include issues related to third-party scanners, Mimecast relaying, and incorrect or non-existent recipient addresses (as per Microsoft documentation and community discussions). Configuration problems with recipient domains, DNS issues, domain blocking, authentication failures, and potential blacklisting of sender IPs also contribute. Resolution strategies range from verifying recipient email addresses, MX records, and authentication settings to checking sender IP reputation and ensuring recipient mailboxes are properly configured and accepting emails.
Key opinions
- Third-party scanners: Integrated third-party scanners with online Exchange can reject emails.
- Mimecast relaying: Bounces can occur during the Mimecast relaying process.
- Invalid addresses: Non-existent or incorrect recipient addresses cause the error.
- Domain configuration: Recipient domain configuration issues lead to rejections.
- Authentication problems: Authentication failures and domain blocking can trigger the error.
- DNS/SPF issues: DNS issues and incorrect SPF records contribute to the problem.
- Blacklisting: Sender IP blacklisting can cause delivery failures.
Key considerations
- Address Verification: Always verify the recipient's email address for accuracy and typos.
- MX Records: Ensure MX records are correctly configured for proper email routing.
- Sender Reputation: Check sender IP and domain reputation to avoid blacklisting.
- Authentication Settings: Review and correct domain authentication settings (SPF, DKIM, DMARC).
- Mailbox Status: Confirm that the recipient's mailbox is active and accepting emails.
- Third-party Interference: Investigate potential interference from third-party email scanners.
Marketer view
Marketer from Email Geeks shares that the bounce is actually a non-existing address according to Microsoft documentation.
21 Apr 2025 - Email Geeks
Marketer view
Email marketer from Spiceworks discusses troubleshooting the 550 5.4.1 error, advising to check for DNS issues, ensure proper SPF records, and verify the recipient's mailbox is accepting emails. They also suggest checking if the sending IP address is blacklisted.
3 Mar 2024 - Spiceworks
What the experts say
4 expert opinions
The 550 5.4.1 'Recipient address rejected: Access denied' error in O365 accounts can stem from several sources. It may indicate Proofpoint being involved, potentially identifying the email as spam rather than simply an unknown user. Further contributing factors include invalid recipient addresses, the sender's IP or domain being blacklisted, the recipient server experiencing issues, inactive mailboxes, or email restrictions. Actions to take include verifying recipient addresses, checking sender IP reputation, retrying email delivery and checking that a user mailbox is not inactive.
Key opinions
- Proofpoint Involvement: Proofpoint could be the cause of the bounces behind an O365 MX.
- Spam Blocking: The bounce might indicate a spam block, not just an unknown user.
- Invalid Recipient Address: The recipient address may not be valid.
- Blacklisting: The sender's IP or domain could be blacklisted.
- Server Issues: The recipient's server might be experiencing temporary issues.
- Inactive Mailbox: Inactive mailboxes can cause this error.
- Email Restrictions: Email restrictions placed by the recipient's server may be in effect.
Key considerations
- Address Verification: Verify the recipient's email address for typos and validity.
- IP Reputation: Check the sender's IP reputation to ensure it is not blacklisted.
- Retrying Delivery: Retry sending the email later in case of temporary server issues.
- Mailbox Check: Ensure the recipient's mailbox is active and able to receive emails.
Expert view
Expert from Word to the Wise explains that a recipient address rejected error occurs due to a number of reasons, this includes an invalid recipient email address, an inactive mailbox, or email restrictions in place by the recipient's server.
23 Jul 2022 - Word to the Wise
Expert view
Expert from Email Geeks explains that she previously tracked the bounce and believed it was Proofpoint behind an O365 MX.
29 Oct 2021 - Email Geeks
What the documentation says
4 technical articles
The 550 5.4.1 NDR in O365 arises from recipient-side issues or misconfigurations, as highlighted by Microsoft documentation. These issues include improper email server setup, sender domain blocking, or incorrect recipient address configurations. Utilizing Directory Based Edge Blocking (DBEB) can also trigger the error when a recipient isn't in the directory. TitanHQ notes this code signifies a permanent error indicating refusal to deliver, even if the email address exists. Resolution involves verifying addresses, ensuring active mailboxes, checking MX records, and reviewing server configurations.
Key findings
- Recipient Configuration: Issue stems from the recipient's email server configuration.
- Sender Blocking: The sender's domain might be blocked by the recipient's server.
- Incorrect Address: The recipient email address may be incorrect.
- DBEB: Directory Based Edge Blocking can cause the error for non-directory members.
- Permanent Error: 5xx codes mean a permanent error, 5.4.1 means the destination server refused delivery.
Key considerations
- Address Check: Ensure recipient's email address is correct and without typos.
- Blocking Verification: Verify that the sender's domain is not blocked by the recipient's server.
- Mailbox Status: Check that the recipient's mailbox is active and accepting emails.
- MX Records: Confirm that MX records are correctly configured for the domain.
Technical article
Documentation from Microsoft Support provides several solutions to fix email delivery issues, including the error 5.4.1. It suggests checking the recipient's email address for correctness, verifying that the sender is not blocked by the recipient, and ensuring that the recipient's mailbox is active and accepting emails. They also advise checking the MX records to ensure correct configuration.
27 Sep 2024 - Microsoft Support
Technical article
Documentation from Microsoft Learn describes using Directory Based Edge Blocking (DBEB) to reject messages for invalid recipients at the edge of the network. This prevents NDRs from being generated for non-existent addresses, improving email security and efficiency. It can cause the error if a recipient is not in the directory.
26 Mar 2022 - Microsoft Learn
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