In <20050822232646(_dot_)GA22558(_at_)primefactor(_dot_)com> Mark Shewmaker
<mark(_at_)primefactor(_dot_)com> writes:
That is, the spf1 spec could consider, if there were no spf1 record
for a domain, that there be a default assumed spf record of: "v=spf1
mx -all", meaning that compliant receivers would drop all mail that
didn't come from the incoming mail servers from non-spf-publishing
domains.
Meng, and others, have widely recommend using a default SPF record of
"v=spf1 a/24 mx/24 ptr ?all". I haven't heard too many objections to
it. (I don't directly support it in libspf2, but it could still be
done with libspf2.)
-wayne