Issue: an unknown error has occurred in outlook. mail could not be sent. the message has been moved to your drafts folder.
Issue detail:
User A has full access on user B mailbox. have migrate User B mailbox to Exchange 2019 recently, but User A was still on Exchange 2013. After that the issue was started (User A was unable to send email from User B mailbox, of which he has the rights)
Before migration of user B mailbox, there was no issue, User A was able to send the emails from User B.
Solution:
Did two things to resolve this issue:
- migration User A as well to exchange 2019
- Assign the permission again on User B to user A.
