[Exchange Web Services] Sending email failed due to the following error: The user account which was used to submit this request does not have the right to send mail on behalf of the specified sending account., Cannot submit message.
Did you solve the problem? I got the same…
Sounds like is possible your from email address in your account setup is different than your login so not allowed at the SMTP server end.
See @Gary post in this thread with an exchange setup where it has that error when sending.
Thanks for your reply, but that was not the problem.
Anyway, it solved itself. Really strange, but for now it’s working.