Domain Forwarding with Domain Mapping Plugin

Instead of using an "A Record", will the domain mapping plugin properly map a "Forwarded" domain?

The domain host of some of my users provides easy "Forwarding". It works good for forwarding to the recepient site, but not for login. Example: forwardeddomain.com/wp-admin does not work for login to newsite.com/wp-admin)

Thanks!
Chuck S.