[Exim] persistent failure with msn.com

Hello,

I'm having an ongoing & persistent problem with my Exim 3.36 server
sending mail to msn.com. I've never had a problem before but for the
last week or two their system is not accepting my smtp calls.

I've cleared the hints files in the db to send fresh with my tests and
the consistent error I'm getting is the "connection refused after
initial connection." Here's some pertinent entries from a -d9 smtp
attempt to a verified and valid address (I've substituted my friend's
username with "validaddress"):

Connecting to smtp-gw-4.msn.com [207.46.181.13.25] ... connected
ok=0 send_quit=0 send_rset=1 continue_more=0 yield=1 first_address=558664
set_process_info: 23367 delivering 18oTBW-00033s-00: just tried
smtp-gw-4.msn.com [207.46.181.13] for validaddress@???: result DEFER
LOG: 0 MAIN
Remote host smtp-gw-4.msn.com [207.46.181.13] closed connection after
initial connection


I can't seem to get any more information about *why* it's closing the
connection. It doesn't seem to even be getting to EHLO or any other
part of the smtp dialog.

Any idea what might be going on or how I might be able to get more info
as to what's going on?

Thanks!
Todd