New bug in POP3 implementation in Outlook 2016 removes emails
On the other hand, if this option is disabled, then letters are duplicated.

Microsoft is still thinking about a solution to the problem, and as a workaround, it recommends rolling back to the previous version. To do this, disable automatic updates in
File->Office Account->Update Options, and then run the command from the command line C:\Program Files\Common Files\Microsoft shared\ClickToRun\officec2rclient.exe" /update user updatetoversion=16.0.6366.2068Another option is to use IMAP instead of POP3.