I have been having some trouble with my Exchange SMTP server recently.
My current trouble is coming from our Sage MAS 200 installation. I disabled "Anonymous Access" on the SMTP server, and have Basic Authentication + Integrated Windows Authentication enabled.
When trying to email out from MAS, I used a specific domain account (mailman) and send from pre-defined emails (in this case it happens to be Orders). The program connects to the SMTP server (I can see this in the error log) but stops with this message:
454 5.7.3 Client does not have permission to Send As this sender.
I can send from the domain accounts own email (mailman), but anything beyond that kicks the error message. I've added the mailman account into the Authentication "Users", but still no luck.
If I'm not mistaken, what I'm trying to do is let this program (Sage MAS200) use our SMTP server as a relay. I'm trying to balance that with having the best security settings possible. I would greatly appreciate a hand with this!