To avoid going to POP3 and putting up with all its limitations, having to do periodic manual cleanouts, etc, you could just not delete them on the phone. If you don't want a lot of email on the phone just set it to sync a small number of emails, maybe 25 or even less, whatever works for you. No need to change a anything on your computer that way either.
Or, some email clients, for example AquaMail, offer the option to send deleted mail to a Deleted folder, where they are still available, delete immediately on the server or hide them in the app but keep them on the server.
You have lotsa options with IMAP.
Android since v1.0. Linux user since 2001.