proxyaddresses same as external Mail URL - ERROR 550 5.1.10 RRS feed

  • General discussion

  • Hello everybody

    We migrated from Exchange to 0365. The old domain was, and it's still available in the proxyaddresses attribute. It's temporary used for receiving mails via popcon.

    If a user sent with the new domain to user(at),  which is external, I received the error 550 5.1.10.  Mailbox cannot be found on exchange or O365. That's logical because the mailbox is an external mailbox. But is also added as accepted domain.

    Can you help me? Is there any solution.

    If you need some more information, let me know.

    Best regards 
    Friday, November 25, 2022 11:28 AM

All replies

  • Tips to fix a 550 error-
    Check for email address typos. 
    Check whether the email IP is blacklisted. 
    Try sending the email after some time. 
    Try changing your outgoing mail port.
    Check whether IP filtering is enabled.
    Enable SMTP authentication. 
    Troubleshoot the SSL method. 
    Contact your ISP.


    Rachel Gomez

    Monday, December 12, 2022 5:13 AM