No changes made to Domino nor WAN environment.
Unable to send or reply to a particular domain.
Here is an example of data within log
03/02/2007 11:17:00 AM Router: Transfer to server PRECOAT.COM is ready with 1 messages
03/02/2007 11:17:00 AM Router: [0000003B] Transferring mail to domain PRECOAT.COM (host PRECOAT.COM [64.216.194.66]) via SMTP
03/02/2007 11:17:00 AM Router: No messages transferred to PRECOAT.COM (host PRECOAT.COM) via SMTP
03/02/2007 11:17:05 AM Router: Error transferring message 005EEEFF via SMTP to PRECOAT.COM OF6823A88B:5D8CA8F5 ON86257292:005EEEFF 500 Command EHLO not known.