Hi @Benard Mwanza ,
Please let me know if all emails cannot be sent to the user's mailbox or only for approval messages.
Was the message successfully delivered to the Exchange server?
Did the sender receive an NDR message?
If the sender does not receive the NDR, it may indicate that the message was not delivered to the Exchange server.
You can use mxtoolbox to check if the sender's IP address or domain is blacklisted.
If the message was delivered to the Exchange server, but not to the user's mailbox.
Then check to see if there are any records in the message tracking log. get-messagetrackinglog.
And check the Inbox rules or transport rules to see if rules are configured to block or reject certain messages.
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