[Mimedefang] OT: Blocking because of MX to 127.0.0.1

[WBrown at e1b.org]

mimedefang-bounces at lists.roaringpenguin.com wrote on 03/09/2004 09:57:01 
AM:

> One of the US ISP (Ameritech - now SBC) blocks mail if one of the MX 
records 
> points to 127.0.0.1 (which as you know, some people do to have fun with 
the 
> spammers who get blocked at the primary mail hub - so they send themto 
la la 
> land on the next preference record up the stack.)
> 
> I can't email anyone at SBC as the mail bounces back because my 
> lowest pref MX 
> record points to localhost.
> 
> Has anyone else seen ISP's who block because of this?
> 
> Are they being stupid or am I?

They aren't being that stupid.  We got hammered a while ago by a message 
that had the same setup.  It couldnt be delivered to the intended 
recipient, so we tried to return it.  The return path had 127.0.0.1 as its 
lowest MX record, so it kept looping. This is more of a DoS than spam.

Our solution was to block incoming connections from 127.0.0.1 on the 
servers.  Is there ever a need to accept TCP connections from localhost 
for mail?