There are currently two POPFile mailing lists. Both are generally low traffic and both are read-only. To subscribe to one of the lists, send an email to minimalist[at]getpopfile.org with the subject “subscribe list” where list is either popfile_commit or popfile_announce. You will receive a response mail that will ask you to reply to it. When you sent the reply, you are subscribed.
Each time one of the POPFile developers commits something to the POPFile source code repository, a mail is sent to this list. Subscribe to it if you want to be informed about the developement of POPFile.
This list is used to send out announcements about new releases of POPFile to interested parties. Subscribe to it if you want to stay up-to-date about new POPFile releases (and possible security holes).