On Mon, May 20, 2013 at 6:44 PM, Keith Moore
<moore(_at_)network-heretics(_dot_)com>wrote:
p.s. I wonder if the problem you describe might at least partially be
caused by DNS proxies and interception proxies, including but not limited
to those incorporated in consumer-grade routers.
Given the funny things some firewalls used to do to SMTP sessions, I
suggest tossing firewalls into that list.