Mike Elliot of MSen.com sent me some data about SPF usages vs SenderID
usage.
Mike published the following records for MSen.com
msen.com. TXT "v=spf1 a mx include:mx.msen.com include:log.msen.com -all"
log.msen.com. TXT "v=spf1 +exists:%{l}.%{o}._spf.msen.net
exists:I.%{i}.F.%{s}.H.%{h}._spf.msen.net -all"
msen.com. TXT "spf2.0/pra -exists:praI.%{i}.F.%{s}.H.%{h}._spf.msen.net ?all"
So, with these tracking exists: mechanisms, he has been able to
determine how often people are using his SPF records and how often
they are using his SenderID records.
Over a ten day period, he found only 2 hosts checking the SenderID
record, but 1082 hosts that were checking SPF records, over a factor
of 500 more. The number of queries were, not surprisingly, about a
factor of 500 more for SPF also.
Interesting data. Not a very large survey, but still more data than
is generally published in whitepapers or presented in summits.
-wayne