User search function for 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 the 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 let me know if this is doable.

Current setup

Three trusted domains CA,MEA,Everest which each domain houses its own open fire server. Users are able to communicate to user on other openfire servers by typing the user name and server name. The search function works great for searching for users in the local domain openfire server , but does not search beyond that.