Remote server returned '554 4.4.7 <domain.com #4.4.7>'

Question

Out of the blue, customers have stated they cannot send emails with attachments anymore; when they previously could. If it were a size limit or file type error, the NDR would point it out. But this NDR has me stumped:

Generating server: [customer's server] [******@mydomain.com] [mydomain.com] Remote server returned '554 4.4.7 <mydomain.com #4.4.7>' Return-Path: <cusdtomer's email> Received: from pps.filtered blah blah blah...

Answer 1

Hello @Aurelius,

Welcome to our Q&A forum！

Based on the NDR you provided, the error message "554 4.4.7" indicates a delivery error and the target email server may be unable or unwilling to accept the email, resulting in a temporary 4_.x.x_error code from the target email server.

May I know if the problem is happening to recipients of a specific domain or all domains？If this error only occurs in emails sent to a specific domain, it is more likely to be related to the target domain.

It is recommended that you use the information in the NDR to contact the recipient's IT department and the recipient's email administrator will need to investigate the issue, which may involve anti-spam settings and security policies or network connectivity issues.

In addition, it is recommended that you check the MX records of your domain to ensure that the configuration is correct. You could use the nslookup -type=mx domain.com command or other online tools to test.

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