not seeing IMAP folders when logged in with 2nd shortname

When the Mozilla Thunderbird mail client connects to Cyrus IMAP in OS X Server 10.3 with a user’s second shortname, it does not see the user’s IMAP folders. Instead, a 2nd empty Cyrus account is created for the second shortname.

Apple’s Mail App and MS Entourage are able to connect with the second shortname and can display all the IMAP folders of the primary shortname (the unix username).

Of course the solution is for the user to use their real unix username to connect.

This may be a Thunderbird issue, but I’m curious as to why some mail clients can authenticate with the second shortname while others can’t..