Hi blakstarz,
According to your description, do you mean you are using Outlook for Mac 2016 and cannot find the messages you have read?
As far as I know, Outlook will not automatically move or remove a message after you read it. In your situation, please try going to View > Filters, make sure the Unread is not checked:
Hope this can be helpful. Please feel free to let me know if you would like further assistance on this.
Best regards,
Yuki Sun
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