Probably. Either there's an existing plug-in, or you can probably easily write one yourself.

To get help on qpsmtpd, you can either consult the mailing list and its archive, or ask questions here on the wiki, from where your questions and the community's answers will hopefully be transferred to this faq.

There's a how-to available.

There is an issue tracker for qpsmtpd at google and you can also report bugs on the mailing list. It isn't quite clear which is better: Usually you get a quicker response at the mailing-list, but sometimes bugs reported on the list are forgotten if they cannot be fixed immediately.