If you want a bit of a trick to NOT have to subscribe to the lists, you can find out the email address per list at
http://lists.openbsd.org, from there can find the list, find the email address and just email to it.
To check responses
http://marc.info @ openbsd-pf is where they get posted (and nabble and some others too) and you can view the responses, then you can actually email yourself the response, and respond yet again to that. Of course @openbsd-pf is one of the few missing from the web GUI ...