I have an exchange 2010 setup within 2 sites. Both sites have 1xEdge, 1xHub/CAS and 1xMail.
I have them setup with DAG so it will failover to site 2 if there is an issue at site 1.
The error I get is that the mailflow is getting stuck at the HUB level. Please see screenshot.
So with the servers off at site 1 (COL) when it fails over to site 2 (BRT) the clients can open outlook fine with the connectors pointing to the correct site hub server but mailflow is either sitting in shadow redundancy or smtp relay queues.
As soon as I turn on the hub server on site 1, with the databases on site 2 everything works fine.