Strange /etc/maillog entries

For exactly two of my users, I get these 'User not found' entries in my /var/log/maillog

The strange thing is that, they're able to check mail via POP just fine. They just get this extra line in the log saying 'User not found'. Here's a sample from the log.

Dec 31 13:17:53 bayview1 cpanelpop[31026]: User not found user=ksmith homedir= passwd=/etc//shadow
Dec 31 13:17:53 bayview1 cpanelpop[31026]: Login host=adsl-068-016-164-206.sip.jan.bellsouth.net ip=68.16.164.206 user=ksmith realuser=ksmith
Dec 31 13:17:54 bayview1 cpanelpop[31026]: Session Closed host=adsl-068-016-164-206.sip.jan.bellsouth.net ip=68.16.164.206 user=ksmith realuser=ksmith totalxfer=181

Any ideas what these are trying to tell me?

 

Thanks phantom. That clears up the bogus entries.

I still don't understand why I was able to retrieve mail while logging in without the @domain.com on the end.
But, all is well.