[Dovecot] Can I block dovecot from deleting read messages, after being fetched?

Hi all, Is there an option to disable (server-side) the deletion of read mails after fetching them via POP3, regardless of the MUA config?

Here are the issues I'm facing:

• my boss wants to force everyone into a server-side "no delete message"-policy, for archiving, auditing and backup&recovery purposes
• the requisite here is pop3, so imap is out
• the mailusers are virtual users (held in a mysql db)
• don't have the budget to set up a separate mail-arvhing server
• don't want to use shaggy ways (aka immutable flag, r/w permissions for Maildirs, etc)

dovecot --version 2.0.15

Help? Thanks!