I received the following from AT&T/BellSouth:

  Dear Mr. Lauterbach,

Thank you for contacting AT&T Internet Service Email Support.

I sincerely apologize for any inconvenience this issue may have caused.
Based on the information you have provided, it seems the issue is due to
not being able to receive emails from  vanagon@gerry.vanagon.com.

It is never the intention of the AT&T Postmaster staff to intentionally
block legitimate mail. As a result of careful yet vigorous anti-spam and
abuse measures, it is a rare but unfortunate occurrence that we would
like to rectify as soon as possible with your help.  You will need to go
to the following website  http://att.net/block_alert fill out the
request information.

Again, thank you for this opportunity to address your concerns. Help is
just a click away! Solutions to common technical problems, answers to
frequently asked questions, and real-time chat with a AT&T eAgent are
all available online at http://support.att.net You may also call us
anytime at 1-888-321-2375.

Sincerely,
A. Cross

AT&T Broadband Email Support

AT&T(R) FastAccess DSL Service 888-321-2375
AT&T(R) Dial Internet Service 800-436-8638