Exchange 2003 queue states "retry" and will not unfreeze to state "Ready"

My issue in particular related to the decommissioning of a Exchange 2003 server.  This server was turned off; then another Exchange server stopped sending/ receiving emails.  However, all other Exchange instances were working correctly.

Cause was tracked down to the "Smart host" settings entry referring to the decommissioned server.

Exchange server> Protocols> SMTP> Default SMTP Virtual Server > Right click Properties

Delivery Tab > Advanced > "Smart Host" entry

In my case i could simply remove the entry as it was not required.