I've recently completed a migration of SBS 2003 to SBS 2011 without two many hiccups.
Server has been running nicely for the past 2 weeks and just today has lost the ability to send external mail.
Mail coming in is no problem at all, ports 25 and 587 open and accepting.
When I'm trying to telnet out on either port 25 or port 587 I can't seem to get any communication - nothing will talk back.
I've created a new Send Connector, and have used a smarthost just for testing.
This send connector is sitting on port 26 and communication is working perfectly.
This is purely a workaround.
The error when I switch back is:
451 4.4.0 Primary target IP address responded with:"421 4.2.1 Unable to connect." Attempted failover to alternate host, but that did not succeed. Either there are no alternate hosts, or delivery failed to all alternate hosts.
Windows firewall is not on, and Wireshark demonstrates that DNS can see the external party...
192.168.4.10 220.127.116.11 TCP 62 15074 > 26 [SYN] Seq=0 Win=8192 Len=0 MSS=1460 SACK_PERM=1
Firstly thought that the 2003 server may have had a hand in what was happening, but no routing groups exist from the old server, and nothing I can see in powershell points to it wanting to communicate with the old unit.
Any help would be amazing!!