In <407EA4B9(_dot_)4030506(_at_)vocalabs(_dot_)com> Daniel Taylor
<dtaylor(_at_)vocalabs(_dot_)com> writes:
For domains that cannot publish TXT records:
Publish one of the following as a CNAME record for the domain:
I suspect that most domain that can't publish TXT records also can't
publish CNAMEs.
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"
What I had been thinking of is publishing an A RR with the name
"SPF-use-http" or something and require the A record to have the
address 127.1.2.3 (or some other unlikely value).
The problem with your suggestion is that it would require three
additional DNS lookups each time no SPF record is found.
Maybe a better idea would be to publish an A record like
"spf-default", with an IP address of 127.1.2.x, where x=1 for
"v=spf1 a mx ?all", x=2 for "v=spf1 a mx ~all", etc. We could come up
with a pretty long list of options that way and still only require one
additional DNS lookup.
That said, I still think it would be far more productive to try and
get DNS providers to support TXT records.
-wayne