[Dovecot] Dovecot as a smart IMAP proxy

[Timo Sirainen]

Do you see a use for an IMAP proxy where the proxy would be able to
execute hooks which modify mail contents, such as transparent
encrypting/decrypting mails, or maybe some virus-filtering? It would
need at least some kind of IMAP command/reply parsing capabilities, so
it might be able to do all kinds of other things.

Maybe one potential use case would be Cyrus Murder-like proxying to
multiple IMAP servers to distribute the mailboxes. But that might be
done better as an imap process plugin, or maybe as IMAP mail storage
backend.

Anyway, the reason I'm asking this is because I was asked to add mail
encryption/decryption capabilities to Dovecot's IMAP proxy, but I'm not
sure what would be the best way to handle this. In any case it would be
a plugin or a new binary which is executed instead of imap binary, but
can I do it in a way that would actually be useful for Dovecot project
in general?