What causes the 550 5.4.1 Recipient address rejected: Access denied AS(201806281) bounce error on O365 accounts?

Marketer from Email Geeks shares that the bounce is actually a non-existing address according to Microsoft documentation.

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.

Email marketer from StackExchange explains that error codes can indicate server or configuration problems. You might need to wait until the issue is solved by the receiving side, or attempt to work around the issue yourself by contacting the administrator of the receiving system. As a final measure, you can also contact your e-mail provider so that they can help you resolve the issue.

Marketer from Email Geeks mentions seeing the bounce with Mimecast users, clarifying that Mimecast sends back what it got when relaying to O365.

Email marketer from Microsoft Community suggests that the 550 5.4.1 bounce error can be due to incorrect email address, domain blocking or authentication issues. Recommends verifying the recipient's email address and checking domain authentication settings.

Email marketer from Reddit discusses possible causes for the 550 5.4.1 error in Exchange Online, suggesting that it can be caused by invalid recipient addresses or a configuration issue with the recipient's domain. They recommend checking the MX records and ensuring that the recipient's mailbox is properly configured.

Marketer from Email Geeks suspects the bounce on O365 accounts is due to a third-party scanner integrated with their online Exchange, which is doing the rejecting.

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.

Expert from Email Geeks explains that she previously tracked the bounce and believed it was Proofpoint behind an O365 MX.

Expert from Email Geeks reads the bounce as a spam block, rather than a normal user unknown error.

Expert from Spam Resource explains that a 550 5.4.1 error can indicate the recipient address is not valid, the sender's IP or domain is blacklisted, or the recipient's server is experiencing temporary issues. They recommend checking the recipient's address for typos, verifying the sender's IP reputation, and retrying the email later.

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.

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.

Documentation from TitanHQ explains that a 5xx SMTP error code means a permanent error. They explain that a 5.4.1 error code means Destination address rejected: Access denied. The destination email address does exist, but the recipient's email server has refused to deliver the message.

Documentation from Microsoft Learn explains that the 5.4.1 NDR (Non-Delivery Report) indicates an issue with the recipient's email server configuration or that the recipient's email address is not properly configured to receive mail from the sender's domain. Possible solutions include ensuring the recipient's email address is correct, checking for typos, and verifying that the sender's domain is not blocked by the recipient's email server.