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 we found that the problem was that Microsoft does not allow the FROM address to be different from the primary email address used to log in.
Microsoft’s official word on this as of August 2021:
“…Microsoft 365 does not currently support sending email from an alias or secondary email address. Email aliases can be used to receive emails only. If you want to send email from another email address, you need to create a shared mailbox. The shared mailbox will give you another email address, without requiring another license.
There are several ways to address this issue:
- Use a Shared Mailbox on Microsoft 365 as they suggest
- Our experience has been that Shared Mailboxes CANNOT be used for AUTHENTICATED SMTP so that was not a fix for us
- If you want to send your email through Microsoft 365 programmatically using Authenticated SMTP (like what is required on phpBB), you need to use a fully licensed Microsoft 365 seat. See this Microsoft thread for details.
- Don’t use the alias to send
- Use a different email provider than Microsoft – several other companies do let you send via an alias
In our case we settled on a using an Outlook.com account to send our phpBB forum emails.