GMail doesn't delete mails when POP3 client issues a DELE command for it. Instead they just become invisible for future POP3 sessions, but they still exist for IMAP/webmail. The same could be implemented pretty easily for Dovecot:
- Add a new setting to enable this: pop3_deleted_flag = $POP3Deleted - When DELEting a message, add this flag to the message. - When listing messages, skip all messages that have this flag. - Also hide this flag from IMAP clients(?) Thoughts? Probably 20 lines of new code.