Message Deferred by categorizer RRS feed

  • Question

  • Hi,

    We experienced queueing of messages and error is saying "message deferred by categorizer".

    It resume to normal when we restarted transport service.

    Is this related to Anti-Virus or Active Directory.?



    Monday, June 24, 2013 12:18 PM


All replies

  • Hello,

    The categorizer performs recipient resolution before routing. Th issue may be related to recipient resolution.

    Recipient Resolution


    I suggest you use message tracking to trace your messages.

    Cara Chen
    TechNet Community Support

    • Marked as answer by cara chen Friday, July 5, 2013 9:27 AM
    Tuesday, June 25, 2013 6:36 AM
  • Just bumping this as I had the same issue. Took me a number of issues to track this down to a bad transport agent. I wrote up my findings here: http://tecfused.com/2015/06/15/message-deferred-by-categorizer-agent/
    Monday, June 15, 2015 12:10 AM
  • In our case, we were experiencing "Message deferred by categorizer" on one of our hybrid outbound SMTP servers to Office 365.  Service was restored when we turned on bypass filtering on the MalwareFilteringServer settings for the problem server

    Set-MalwareFilteringServer -BypassFiltering $True -identity <Server Name>

    Larry Baker

    Friday, September 9, 2016 7:59 PM