This behavior might be encountered because of some settings that you made to your Outlook program. To be noticed that some mails might be delivered directly to the Spam folder. You might want to check that folder before proceeding forward. To restore the settings of Outlook to the default state, you need go to to C:\ Users\ Username\ AppData\ Local\ Microsoft\ Outlook. Some files might be hidden, so to view them, you first need to go to Start and in the search bar type Folder Option and press Enter. In the new window, make sure that Show hidden files option is selected. Once you reached the destination mentioned above, delete all the files from there. Also, go to Start > Control Panel > Mail and delete the profile(s). After you did all this, restart Outlook and set up your account again. You shouldn't experience any more problems with deleted mails.