[exim] Hotmail DNS issue

I do some HELO checks, including checking the server address when *.hotmail.com is in the HELO command. One Hotmail IP address appears to be set up differently from all the others I have checked and it is being rejected by my HELO checks: 65.54.246.99.

My check is that if $sender_helo_name ends with '.hotmail.com' then I require $sender_host_name to also end with '.hotmail.com'. With 65.54.246.99 $sender_host_name is empty.

If I do 'nslookup 65.54.246.99' I get two hostnames returned

s1.bay2.hotmail.com
bay0-omc1-s27.bay0.hotmail.com

The first has no A record, the second's A record is 65.54.246.99.

Some times nslookup returns the hostnames the other way round (but $sender_host_name is ALWAYS empty).

All the other hotmail.com server IP addresses I have tried return a single hostname.

Checking my logs this started on 29th May 2008! I am amazed that this has only just come to my attention because we must have rejected thousands of Hotmail messages because of this in all that time. Because Hotmail use multiple servers for sending, senders will see this problem intermittently.

Can anyone suggest a solution? I don't hold out much hope of telling Hotmail that they got something wrong!

Regards,

Phil.
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Phil Chambers
Postmaster
University of Exeter