Hi Joseph,

I’d like to confirm the following details:
1), Did this issue occur with OWA (Outlook Web App) or Outlook?
2), Have you checked the Deleted items folder, Did your e-mails appear here?

In terms of your situation, I suggest you do the following steps to troubleshoot this issue:
1), Please go to OWA (Outlook Web App) to see if you can find your e-mails. In addition, please check the deleted items here.
To login OWA, log into Office 365 portal, click Outlook on the top.

2), The read message may be filtered by some viewing rules.
To find these items, I suggest you  check if there is any filter rules with your mailbox.
In addition, you can perform an mailbox search to see if you can find these items. To do this, please refer to  Search for an Item.

If you have any additional questions, please feel free to post them in the forum.

Thanks,
Evan Zhang