2nd Exchange to accept some mail from 1 domain and all mail from another

My company is interested in bringing up another exchange server for one of our remote sites. We have a point to point setup between offices and another T1 internet gateway out at the remote office. I would like to know if I can have our primary exchange handle certain employee mail from Domain A, and have the remote exchange handle mail for certain employees from Domain A, and all of Domain B. I am sure it’s possible, but I’m not sure how to work it. Also, if you have an alternative solution to this, then I would welcome the thought.