Problems with Hotmail deleting incoming mail

[Andrew Daviel <advax () TRIUMF CA>]

A little while ago we had some compromised webmail accounts sending a few
thousand spams before we caught them (I since installed the squirrelmail
restrict_senders plugin, which caught another one).

At the time of the compromise, Hotmail blocked us (SMTP 5xx status) as
the spam used a live.com sender address so they got backscatter as well
as some direct spam. Perfectly understandable. I got a live.com
account to check https://postmaster.live.com/snds/ipStatus.aspx
and could see the stats. Now clear.

Since then, Hotmail seems to have been accepting mail from our server
(2xx status) but then discarding it. After some experimentation with a
test account, it seems that a reply to mail from a Hotmail customer might
get through, but not an "unsolicited" message. The mail seems to just
disappear, not turn up in the junk folder.

I wondered if anyone else had had these issues. It seems almost
irresponsible, just discarding legitimate email with no warning.

Microsoft support is asking us to sign up for all sorts of whitelist,
SPF, sender ID programs plus their Junk Mail Reporting Partner Program,
as if we were a commercial bulk mail provider, before wanting to look at
the problem.

Has anyone done any of this stuff ?

--
Andrew Daviel, TRIUMF, Canada
Tel. +1 (604) 222-7376  (Pacific Time)
Network Security Manager