[Dovecot] director: non standart ports at backends

[Костырев Александр Алексеевич]

hello,
I'm trying to figure out how to proxy pop3 and pop3s that listens on 
non-standart ports at backends.
For example, pop3 is at 1110 and pop3s at 1995 (on backend side).
is it possible? 
how should I separate this ports in director's config?
it's easy for one port:
for example lmtp - you just use passdb in protocol lmtp {}