For domains that cannot publish TXT records:
Publish one of the following as a CNAME record for the domain:
spfdefault-weak
spfdefault-soft
spfdefault-strict
These would indicate the desire but inability to publish
a proper SPF record.
spfdefault-weak would indicate "v=spf1 a mx ?all"
spfdefault-soft would indicate "v=spf1 a mx ~all"
spfdefault-strict would indicate "v=spf1 a mx -all"
I exclude PTR records from this as I assume that if you
can't publish TXT you are unlikely to have authoritative PTR
capability as well.
--
Daniel Taylor VP Operations Vocal Laboratories, Inc.
dtaylor(_at_)vocalabs(_dot_)com http://www.vocalabs.com/
(952)941-6580x203