wip/mxallowd 1.7 NetBSD

mxallowd is a daemon for pf/pflog which implements a slightly improved nolisting mechanism. Basically your nameserver has to be configured to return two MX ip addresses of which one does not run a mail server on port 25 (the one with higher priority). Most spammers try to connect directly to the first mailserver -- mxallowd blocks that. You have to connect to the first one and then to the second one, direct connections do not work. Real mailservers (not spammers) have to try all MX ip addresses in order (sorted by priority) until they succeed in delivering the mail.