If you want to know the cause of AOL mail not receiving emails it can often occur due to a few simple things. These things can be due to either the message being in the wrong folder. Another possible reason for the issue may be the third-party mail client's settings. You can check your account as well, it was deactivated due to inactivity. The first thing that you need to check is your inbox, if you're not getting the missing mail over here then you have to check your other folders to find your mail.