Written by Bill Cole on Apr 7, 2008, at 4:58 PM:

...

Hey folks. One feature I'd really like to see in dovecot is the
ability to point it at a database (with a configurable query) and
have it allow or deny a connection based on looking up the source
IP address in that database.

... much stuff discarded.

I understand that the behaviour requested is similar to that of allow_nets (http://wiki.dovecot.org/PasswordDatabase/ExtraFields/AllowNets) but modified to explicitly deny some IPs (individually or in the range form). If so, probably some of the work should be already done. Sorry, I do not have the programming abilities enough to face this. Incidentally, I would like to notice that I opened a thread a few days ago regarding allow_nets and database (Bill's request needs to make use of an external database too) because I am not able to make allow_nets work properly when using an external DB *and IP ranges*. Maybe Bill would like to block single IPs so this bug? wold not apply to his case if an extension or adaptation of allow_nets is done. (My request, in case someone out there is curious: "Allow_nets + MySQL failing when using range notation")

Regards,

Javier