I have this issue with an SBS 2008 server with Exchange 2007. Incoming mail works fine with no problems but outgoing mail get stuck in queue. The weird thing is if I open server manager and click on hub transport immediately mail will start flowing through.
I do have an issue with http://blogs.msdn.com/b/keithmg/archive/2009/01/06/exchange-topology-discovery-failed-error-0x80040a02-dsc-e-no-suitable-cdc.aspx but I have a problem. Permissions were not the fix. When I enable IPv6 outgoing mail stop immediately and the mail troubleshooter says the server is not compatible with IPv6.
So here I am stuck. :(
Edit:I have disabled IPv6 in the router