Our users send emails from shared mailboxes and now the boxes are regularly being blocked from sending out email. We use Outlook on the Web.
Error Message: A high-severity alert has been triggered
Activity: Potentially compromised user account
Details: User << Email ID >> has been restricted from sending messages outside the organization due to potential compromised activity. The details give a large number of emails being suspected as spam.
When I go to Sent Items, they are all legit emails.
How do I check which outgoing messages are marked as spams? I suspect it's the number of emails and nothing else that is triggering the event.
Please help. I contacted Microsoft support, but nothing has been suggested to resolve the issue.