@flaxking said in Outlook SMTP Non-Compliant Sender Address:

Hmm, I just got the same when testing using telnet

550 5.7.1 Non-Compliant sender address. Code : -4

Oh, good info! Thanks.

I have and every time I have to rebuild both profiles. It is intermittent though and I still haven't figured out what actually causes it

Real solution... Stop using outlook and push to OWA.

When we've seen this issue it's usually been saved credentials in Windows credential manager. For some reason they can authenticate but then Outlook randomly tries the credentials in credential manager. If the credentials are old you will get a login prompt. That's always the first thing I check.

This is rather frustrating.

User Account setup completes normally, but when you open Outlook it asks for a password repeatedly. When you hit cancel you get this 'error'..

I found another KB which didn't do any better either.

MS2010o365.png

Dispatch seems only to 'mirror' my main account...