[Dovecot] Feature request: Force leave copy on server

It would be very nice, if I could force users to leave a copy on the
server when using POP3. This is because users primarily use a web
interface to access mail (the web interface uses IMAP), but users can
also download messages using POP3.

Users who forget to set the "Leave copy on server" get all their
messages deleted in the web interface, and mostly they don't want
(expect) this behavior. Isn't it possible to create another way to tag
POP3 messages as deleted without these being deleted in IMAP?

Sincerely, Bardur Haskor