Windows – MS Exchange Transport Service won’t start after IP stack reset

It would depend heavily on what is in the queue. It's possible you're being spammed relentlessly. It's also possible that you are receiving a lot of non-delivery notifications, or that you are sending nondelivery notifications to the queue. In either of these cases, you might have a lot of nondeliverable mail in the queue, but depending on your configuration it may sit there for days until it is purged.

Check the hub transport logs. They will tell you what it is thrashing about doing.

Exchange needs to be able to select ONE receive connector for every incoming connection.

It checks two parameters for the incoming connection:

1. The IP port number the connection is trying to reach. And

2. The IP address the connection is coming from.

In order for the transport to run correctly you need to ensure that no two connectors conflict on those two parameters.

So in your case the "Default Frontend" connector is already bound to (port 25 AND any address) and now you add another custom receive connector bound to (port 25 and some specific addresses). These two conflict because for the specific addresses they would both want to be responsible and that causes your problem with the transport service.

Solution: Please exclude the specific addresses that you configured in your custom receive connector from the Default Frontend connector scoping.