So i found a method called Preauth which is suppose to allow me to allow a link to pass between a trusted domain and Zimbra allowing a login. however have a PHP Portal and was wondering if there was a different way to allow me to let users click a 'Mail' link and have the portal pass information to Zimbra via a simple link. so there would be something like http://mail.domain.tld/?user-=me&pass=you
which would log me in. and allow the user to just have to login to the portal and not zimbra aswell.