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Email To/From Microsoft Distribution Lists failing

My organization uses Microsoft 365 with Sophos Central Email Security as the email filter.  The DLs contain both internal and external email addresses, such as Gmail or Yahoo. When I send email from an internal address to the DL, everything gets delivered.  When an external address sends to the DL, the internal addresses receive but the external addresses fail.

I cannot see any error messages from within Sophos.  The external reject message is


550 5.7.1 XGEMAIL_0011 Command rejected

Message rejected by:

This is a problem for my organization.  Any tips/help?

Added TAGs
[edited by: Raphael Alganes at 12:57 PM (GMT -7) on 17 May 2024]
Parents Reply
  • Steve/Stuart, one of the initiatives we are working on is the ability to show a consolidated quarantine where you can see what Microsoft has put into their quarantine along with the ability to release messages from the Microsoft quarantine. As Microsoft made the Secure by Default hard stance last year, i.e. if your mx points to then you cannot disable Defender Spam scanning. We do have thousands of customers using mailflow mode without issues but you have to decide what works best for your organization.

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