Using classic Outlook for Windows in business environments
Dear Daryl Neill,
Thank you for posting in the Microsoft community.
According to your description, the sender to your address received a bounce-back email. Please correct me if I misunderstand.
For this issue, please log in to the Outlook web version (outlook.live.com), click on the gear settings icon in the top right corner - Mail - [Rules] & [Forwarding and IMAP] to check if there are any relevant settings that may have caused this problem. If any unknown forwarding or forwarding rules are enabled, please remove them.
We appreciate you spend your time working on this issue. Feel free to post back if you need further assistance. I wish you all the best.
Best Regards,
Ulrica.W - MSFT | Microsoft Community Support Specialist