Hi All,

I have a strange email problem with my server and I'm hoping someone can point me in the right direction.

I have SBS server with Exchange 2003.
This deals with emails for 2 domain names, domain1.co.uk & domain2.co.uk
The A records for each domain name point to the same External IP address (the firewall device).
The PTR record for that same ip address points back to mailgate.domain1.co.uk

I have a problem where a few senders are getting their emails bounced back after 6 hours saying "A message that you sent has not yet been delivered to one or more of its recipients after more than 6 hours on the queue on mail10.atlas.pipex.net

Now, I can replicate this fault. I have an email address for a domain that is hosted with 123-reg, and I have it set up in 2 different locations (home and work). Same incoming and outgoing settings in outlook at both locations.
If I send an email to xxx @ domain1.co.uk from either location (home or work) they are successful.
If I send an email to xxx @ domain2.co.uk they are successful only when sent from home. When sent from work, they bounce back with the delayed message.

Now this same problem is happening to quite a few senders who are trying to send email to xxx @ domain2.co.uk, so it cant be down to the sender.

Also - with the test that I replicate, I dont ever get any similar messages from any other people that I try and send to.

From all this information, I conclude that something on my SBS server is rejecting emails based on how they are being routed (not on the address).
Obviously I cannot control any of the settings on any of the people who are trying to send me email, so there must be an issue at my server's end (or the ISP)

Does anyone have any idea what is causing this problem?