Some questions with WebExternalAuth

Hello,

My users create tickets via a web form that i then send to the mailgate.

I would like to give my users access to the web interface to view their open
tickets.

In our system we already authenticate them, So from what i am reading, if i
set the REMOTE_USER var to their email address and set WebExternalAuth to
??? then it will let them in??

Is this a correct assumption. Is there any docs that help with this?

Thanks
Randy