In this section you can read about various mail servers/MTAs (mail transfer agents) that does not function properly with greylisting (ie. it does not, as expected and according to the standards, resend messeges that was greylisted).
There is a bug in MS Exchange 2003 when sending to greylisting servers.
Sometimes the server will fail to re-queue messages sent to some servers
that implement greylisting. More information:
groups.google.com/group/mi...64d5749ee7cb
groups.google.com/group/mi...07ac14b116db
According to ozinm on our forums there is a possible hotfix available from Microsoft now: www.greylisting.org/forums/showthread.php?tid=18