Comcast email bounces

[jc at trillian.mit.edu (John Chambers)]

Starting Saturday, my wife (Shelley) started seeing a lot of email to
comcast  customers  bounce  back  with  a message saying that we were
abusers. Our ISP is speakeasy, and she managed to talk to a CS person
on  Sunday  who told her that comcast had been doing to this to email
coming via at least one of speakeasy's servers, but not all of  them.
I  verified  that  the  comcast  message headers identify a speakeasy
server address as the abuser, not our address.

Has anyone else seen this? Any ideas about a workaround until it gets
fixed?   The  speakeasy  people  don't  seem  to  know of any.  Their
suggestion is to keep trying until you  get  a  server  that  comcast
isn't blocking.  I did a bit of digging to get some better ideas, but
it seems that speakeasy only  advertises  mx.speakeasy.net  as  their
mail server, with some hidden magic parceling out the messages to the
real servers.  This doesn't seem to provide an obvious way  to  avoid
the problem.