Using older versions of Outlook for Mac in business environments
Hi Maev C
Thank you for posting in Microsoft Community.
May we confirm what account you're using in Outlook? (Exchange/POP3/IMAP)
Please try to search for any of the missing mail using the search feature in Outlook to see if the mail appears when searched for.
By default, Outlook collapses the folder listings in the left column, please try to click on the expansion arrow next to On My Computer so see all of the individual folders.
Kindly navigate to Outlook > Preferences > General, then select Show all account folders, incase the sent items folder is hidden.
Best Regards,
Momo