Exchange 2013 and 2007 coexistence and redirects

Hi all,

I'm settings up the coexistence but i've got a problem.

I've got 3 sites:

Site A: Exchange 2013 cas and mailbox

Site B: Exchange 2007 hub/cas and mailbox

Site C: Exchange 2007 hub/cas and mailbox

The problem is the owa and active sync redirect. I can open a mailbox located in site B where the legacy.domain.com dns record points, but i cannot open a mailbox from the exchange 2013 nor 2007 owa from site B to C.

I configured only the internal url leaving the external one blank.

How do i redirect all the requests to a mailbox located in site C from site A and B?

Thanks,

D.