My company is a late bloomer and we're finally moving from 03 to 07. Currently we have two 03 boxes (exA and exB) which have been working just fine for quite some time. I just setup an 07 box (exC) with all the roles. A user on exC is able to send/receive anyone on internet and anyone on exA. The same user can receive from anyone on exB but they cannot send to anyone on exB.

Under the old esm 03 console under first administrative group, I can see exA and exB as members in the routing as they should be. I also see exA and exB in a routing group under the new Exchange Administrative group that was created on install. I assume the issue is that there is no routing group containing exB and exC. So my question is, to get exC users to email exB users, do I need to setup a send connector on exC or a new routing group connector from the old esm console? If the latter, under which administative group do I configure it as?