Dear Zach Provost
Good day! Thank you for posting to the Microsoft Community. We are happy to help you!
First of all, we regret for the inconvenience caused to your work. Based on your description, I have a general understanding of your question, please first kindly use your account to login OWA(outlook web app) and then check whether your emails got the same issue in outllook web, thanks.
If not, then please kindly try creating a new profile and re-add your account and then check the result, in the process, in order to prevent you from losing important data, please kindly refer to Export items to an archive file in Outlook for Mac - Microsoft Support
Meanwhile, if you got the same issue in new outlook profile, since we specialize in technical support for Microsoft 365 Business Exchange Online, which is not professional for the Outlook for Mac, in order to better help you and no longer waste your more time. I recommend that you ask for help from our dedicated team, where technical engineers specialize in these related issues, and experts will focus on inquiries to further assist you, for details, please kindly refer to: Contact support within Outlook for Mac
Thank you in advance for your understanding! Your patience and cooperation will be greatly appreciated. I hope all the best!
Sincerely
Kerry Chen | Community Moderator