[Dovecot] Auth checking also the service

[Alex]

Hello everyone. I'm switching to dovecot from courier-imap and after some 
problems with Apple Mail client, now everything seems to be fine.
The only problem that I have not solved yet is to check also the service 
(pop3, pop3s, imap, imaps) in the authentication phase. 
In courier-authlib I do this:

MYSQL_SELECT_CLAUSE   SELECT username, \
                        password, \
                        "", \
                        1002, \
                        1003, \
                        '/vmail', \
                        maildir, \
                        quota, \
                        name, \
                        "" \
                      FROM mailbox \
                      WHERE username="$(local_part)@$(domain)" \
                        AND active=1 \
                        AND $(service)=1

where $(service) can be pop3, pop3s, imap or imaps. Is it possible to do a 
similar thing in dovecot?

Thank you in advance,

Alex