I posted this in the eDirectory forum, and they said to post it here..

Here's one for the books. At this site I'm working at, users are able to
login using username.dnsname to the client. Example -
ryank.acmeschoools.k12.sc.us. Works for all users tested. Not sure why
this is happening. Not really an issue, but I would like to know how this
came to be and if I can turn it off.

Any insight would be appreciated.