Recieving email but outgoing sitting in queue

We have a single Exchange 2010 standard server (Win2k8 Standard R2).  Last nite mail stopped going out.  Everything is simply sitting in the queue.  Some messages were tagged with 451 4.4.0 Primary target ip responded with 421 4.4.2 connection dropped due to timeOUT.

Looks like everything is just stuck.  Can I restart one of the Exchange services to see if it is hung up?  Windows updates were run last week but it seemed to be fine.
cobmoIT ManagerAsked:
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Sure, restarting the services won't flush the queue / delete messages
Restarting the MICROSOFT EXCHANGE TRANSPORT SERVICE will start things moving again if the error is due to an issue with the SMTP service.

It could also be a firewall issue with outbound SMTP.

Do your Firewall logs show anything when your Exchange server is trying to deliver?
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