An MX REQUEST almost always
gives back NS records and A records as well as the MX
ANSWER. All I'm saying is that I think that the best place for the
spf TXT record is in the REPLY to an MX REQUEST.
Since I don't use UNIX much (or Bind at all!) I refer you to
dnsstuff.com/pages/expert.htm which will give you a great
graphical sense of this.
But I am getting the impression that it may not be possible to
add additional records to a REPLY to an MX REQUEST, such as a
txt(spf) record. I do this just be adding a line to my Java DNS server.
Perhaps an addition to a zone file won't achieve this. That is
for someone familiar with it to say. But I do know
that my DNS server with its additional TXT record in REPLY to an
MX REQUEST works perfectly in terms of directing incoming post to the
domain.
geoff
Actually, Geoff, your example is a little off. In the case you give above,
when an MX is requested by a sending server, there is no need for SPF at
that time. On the receiving end, the SPF record is queried, but the
sender's MX is not necessarily needed. As an example, check out AOL's SPF
record. It contains only IP Addresses, so no further DNS queries are
needed. And in the case of my SPF record, you'd have to do an A lookup on
gw.alaia.net. Now, in the case of the DNS server sending the A record with
the MX record, that is simply a convenience. Yes, it would be nice if the
DNS server could understand the SPF TXT record and send back any additional
information needed, such as the MX record or A record, but that's a long way
down the road....
Marc
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