I have this incredibly strange problem with exchange between 4 sites.
I have 4 sites. Each was configured in its own administrative group.
Our main office has a routing group connector for each of the 3 servers in the other offices.
Yesterday I changed the exchange organisation to native mode and since then the offices have had lots of problems sending mail within the organisation.
If I send a blank test message from one of the sites the message will arrive but there are messages in the queue that will not come through.
In the event logs I've seen this event logged once in a while.
Message delivery to the host 'x.x.x.x' failed while delivering to the remote domain '_693a5a4ec6af5d4081f63b043f920e7a_D' for the following reason: The semaphore timeout period has expired.
I also see this log
Message delivery to the host '192.168.0.4' failed while delivering to the remote domain '_693a5a4ec6af5d4081f63b043f920e7a_D' for the following reason: The connection was dropped by the remote host.
I don't see any other logs that would indicate a problem.
When I look at the main servers smtp connector I see sessions from the remote servers, you can see the sessions have been connected for over 300 seconds. Its like the connection is made and then it just stays open.
When sending from the head office server to any of the others it works fine but the other way its very tempremental.
I've run the exchange trouble shooting tool and it reports no problems.
I've using symantec enterprise, I've verified I'm not using internet email scanning plugin.
The server are connected via cisco ipsec tunnels, all ports are good.
I'm really puzzled on this. Like I said it worked fine until I went into native mode and of course. Theres no going back.