Multi-domains support

I was wondering if theirs any capability with in openfire or the spark client to allow users to add users that are housed on another openfire server.using the search function. At the current time inorder to add a user that resides on another domain we have to know his/her user ID and the server the user is placed on. Ideally we would like to be able to search by user name only , with the results give us users on any spark server.

Please le me know if this is doable.

Current setup

Three trusted domains CA,MEA,Everest which each domain houses its own open fire server.