Microsoft Exchange 2003 SP2

Problem: Certain public domain Mail Servers are unable to send e-mail to a Microsoft Exchange SP2 Mail Server.

Or....

A Microsoft Exchange Server SP2 is unable to receive e-mail from a mail server using a customized subnet mask. Such as a /29 subnet (255.255.255.248) or (255.255.255.252) /30 etc.. an example of a full class subnet mask would be 255.255.255.0

Symptoms: If the Microsoft Exchange SP2 Mail Server has Sender ID Filtering enabled and the public domain mail servers have a non-full class subnet mask with a non-full class subnet mask specified in the DNS SPF TXT record the Microsoft Exchange Server running SP2 will fail the SenderID check on the received e-mail message and will not deliver the e-mail message to the intended recipient.

Solution: This can be resolved by installing the Microsoft Hotfix KB910272.


This problem has been haunting me for quite some time. I hope this helps other system administrators who might be frustrated by this problem! Where the majority of the e-mails are received but there's always that one mail server that can't seem to send to your Mail Server. This fix might be for you!