I have a SBS2003 server running both exchange and ISA. About a month ago, certain senders email started to be rejected. They are getting the following message back:
"[xxx.xxx.xxx.xxx] #<[xxx.xxx.xxx.xxx] #5.0.0 smtp; 5.4.7 - Delivery expired (message too old) [Default] '[Errno 54] Connection reset by peer' (delivery attempts: 69)> #SMTP#
I've used the message tracking center to find the emails and they do not exist so I know they are not getting that far. I also had the sender have someone else in his organization send an email to see if we were blocking him for some reason but it appears to be the domain. Messages are not being blocked by the intelligent message filter either.
Only change about the same time was I went from using DynDNS to a static IP address on the DSL modem. I only have one MX record in the DNS and it is pointing to the IP on the DSL modem. I heard of one other sender geting this error too from a different domain, but the majority of mail is coming through with no problem.
I'm struggling to figure out where to look to see why these keep being rejected. Thanks in advance for the help!