Authenticating users with multiple email ids

[odeskonrails]

I have a scenario where in a user can associate multiple emails with his account. We store all the emails associated to the user in a seperate model "UserEmail".

A user will register via google account "[email protected]" (which is authenticated and stored in the users table itself) and add another email say "[email protected]". So we have 2 UserEmail records for the user. Now can you suggest me on how can I authenticate if the user is trying to login with his yahoo id without treating him as a new user (Since the users yahoo id is in user_emails table)? I do not have much experience with authlogic_rpx and this is the first time I am using it.