550 5.7.1 RESOLVER.RST.AuthRequired; authentication required

Weird Exchange 2007 errors. I had a system that was sending updates via smtp but not working. I whitelisted the IP address of the server on the edge server under anti-spam, like you do, but the hub transport started denying the message with “550 5.7.1 RESOLVER.RST.AuthRequired; authentication required”. It took me a while to notice that I was getting the 5.7.1 error on the Hub Transport role rather than the Edge role, as I’ve grown used to having to log into the Edge role to deal with any anti-spam stuff (5.7.1 means anti-spam).

Turns out on the Hub, EMC, Recipient Configuration, Distribution Group, Properties of the Group, Mail Flow Settings Tab, Message Delivery Restrictions, Properties there is a check box for “Require that all senders are authenticated”.

That is far, far too many levels deep for a new default setting.

4 thoughts on “550 5.7.1 RESOLVER.RST.AuthRequired; authentication required

  1. Emporio

    Thank you very much for this post, it addressed the problem we were experiencing.

    What I am confused about though is that we had created about 20 distribution groups at the same time and not all of them appear to have had that options enabled.

    Now we’ll need to determine what is different between the various groups, but in the mean time, thanks again.

  2. S N Ahmed

    Solution : -> On the distribution group go to the tab Mail-flow, open message delivery restrictions and remove Require authentication. So thank you for the lead.

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