Re: [swinog] Nice to know for ISPs: Exchange 2003 SP2 Greylisting bug

Martin Blapp wrote:

We just had a case where we missed some mails from a vendor, and those mails now have arrived with three month delay. After some investigation we found the reason for the delay: the vendor is using Exchange 2003 SP2, which has a known, still unfixed bug. It causes outbound mail to domains that implement greylisting to be jailed in a black hole until the SMTP service is restarted.

I can't believe that even Exchange would be unable to do a retry - there are plenty of situations where a server might return a temporary 45x error.