Question : Unable to send New messages - Exchange 2007

Hello all. I am unable to send new messages. If I reply to an email, it goes out fine, but if I create a new message it gets stuck in the queue.
The error is 4.51 4.4.0 Primary IP Address responded with 421 4.2.1 "Unable to Connect"

Answer : Unable to send New messages - Exchange 2007

Changed the send connector to use the DNS setting on the NIC, and changed the DNS settings on the card to point to external DNS server