Incoming email lost intermittently between SMTP and Domino router

We have intermittent problems receiving mail from a particular domain. The mail is received by SMTP but then somehow never delivered.

One of these instances I tracked it down to the following line in the log.nsf file:

07/21/2009 09:49:10 AM SMTP Server: mta2.srv.hcvlny.cv.net (167.206.4.197) disconnected. 1 message[s] received

which is not followed by a Router statement about this message.

Any suggestions?

Subject: antivirus or server rules?

Do you have any antivirus or antispam products installed that delete or quarantine messages? Perhaps this message is being mistaken for something bad?

Do you have any server rules set up?