554 5.2.252 STOREDRV.Submission.Exception SendAsDeniedException.MapiExceptionSendAsDenied

SOLVED: Microsoft 365 Exchange Email SMTP 1301 <- 554 5.2.252 STOREDRV.Submission.Exception:SendAsDeniedException.MapiExceptionSendAsDenied

After spending quite a few hours trying to correctly configure the email on a phpBB forum (for our Commodore.ca website users) we found ourselves stuck on the following error showing in the logs (Administration Control Panel > Maintenance tab > Error Log): 1301 <- 554 5.2.252 STOREDRV.Submission.Exception:SendAsDeniedException.MapiExceptionSendAsDenied After much research Read more…