On May 24, 2004, at 11:36 PM, John Levine wrote:
A third category is organizations with multiple divisions or locations
that use a single mail gateway. For example, the Oklahoma DOT has a
MX for *.okladot.state.ok.us (along with some CNAMEs for shorter
addresses) that lets them filter all the mail in one place and then
use internal rules to route the mail to the various departments.
Some large ISPs break up their DNS zone administration in similar
fashion to their network boundaries, where their networks are located
in multiple states. The number one source of spam for me comes from
one such ISP, and some of their zones have SPF records and some do not.
For instance, they are bigisp.com (this is the domain used by their
retail/residential customers), but I get spam from
x-x-x.pa.client.bigisp.com and x-x-x.nj.client.bigisp.com where the
former is covered by an SPF record and the latter is not. It would
seem that a wildcard at *.bigisp.com would help them out.
-andy