POP3 doesn't automatically delete the emails it fetched (with RETR). It has to emit another specific command (DELE) for this purpose.
So, keeping or not keeping mails on the server is a matter of configuration in your client. I think all clients propose this choice and some will also add extra options like deleting only after a number of days since fetching.
So, keeping or not keeping mails on the server is a matter of configuration in your client. I think all clients propose this choice and some will also add extra options like deleting only after a number of days since fetching.