[Mimedefang] Black Listed

[Mark Defang]

This may be off topic, but I don't know who else to turn to.

I have been a MIMEDefang user for a couple of years now.  I absolutely 
love it!!  I myself do not use Internet black list subscriptions because 
I have not seen the need to.  Using MIMEDefang, custom rules, 
spamassassin and bayes filtering and uvscan, I have had no real problems 
to speak of.  Using a black list subscription just adds one layer of 
problems that I don't have much control over, example to follow.

To make a long story short, here is my problem.  We have a T1 through 
Ameritech with an IP block of like 16 IP's.  We send email to a customer 
of ours that uses another ISP.  The customer's IP subscribes to an 
Internet blacklist.  Starting today, we, as a domain, can not send email 
to this customer.  When I contacted the ISP, they stated that Ameritech 
had been blacklisted and I needed to contact them to have the issue 
resolved.  Ameritech needs to contact the black list provider and clear 
it up.  AMERITECH!!!

I have a few problems with this...  First, my domain was not the one 
that was blacklisted, according to the ISP.  If, what he says is true, 
every Ameritech customer in the midwest, maybe further, will not be able 
to send email to any ISP subscribing to this blacklist.  This doesn't 
even sound possible to me.  Secondly, my domain was not the one 
blacklisted.  Why would lax mail security on another domain or a 
compromised home user account have any bearing on my ability to send email?

If this is off topic, I apologize.  I am going to pull what hair I have 
left if I have to talk to Ameritech for 16 hours to finally get a hold 
of the correct person to be hung up on...

Thanks!

Mark D.