> For this particular case it would be better to write a DNS plugin that
> would do a DNS lookup for the domain nameservers and return that in a
> matchable form. Going via the registrar to get the nameservers incurs
> far too much overhead.
Two examples with postfwd:
# hard version
id=REJECT_BAD_PW
sender_ns_names=~/\.registrar-servers\.com$/
sender=~/\.pw$/
action=REJECT blabla
# soft version, combine it with a SA header rule to tag the mail
id=TAG_BAD_PW
sender_ns_names=~/\.registrar-servers\.com$/
sender=~/\.pw$/
action=PREPEND X-Postfwd: Bad PW sender
