Do you have any old phones that you synced with POP3? Windows Mobile? Outlook or Windows Mail? Ever connect it to Thunderbird? (Be careful with anything IMAP

Do you have any old phones that you synced with POP3? Windows Mobile? Outlook or Windows Mail? Ever connect it to Thunderbird? (Be careful with anything IMAP, check offline) Can you contact the sender of the email and see if they can get a copy from their sent archive? Ever download a Google Takeout archive? Try Google Takeout anyway? Try POP3 sync, then reset POP3 status and resync?