We have an Exchange 2010 server running on SBS2011. there is one specific domain we are not able to email. looking at the message queue it just sits in a Connecting or Retry status. Eventually getting an NDR message.
I ran nslookup -type=mx domainame and it resolves. I try to telnet and it gives me an error 421 4.3.2 system not accepting network messages... connection host lost
I have verified that GFI (Spam Solution) has the domain in the allow list.