[Dovecot] Strange Disconnect Problem

[Marc Perkel]

It's only happening with one user but for some reason I can't get this 
person logged in. And I'm using his ID on my computer and my ID works. 
Using two different IMAP clients.

What would be causeing the "disconnected" to happen?

dovecot: Oct 17 10:56:43 Info: imap-login: Login: 
user=<lowsley at cbsyellowpgs.com>, method=PLAIN, rip=65.37.192.182, 
lip=69.50.231.10
dovecot: Oct 17 10:56:47 Info: imap-login: Disconnected: 
user=<john at sembrot.com>, method=PLAIN, rip=204.95.16.61, lip=69.50.231.10