can Session Manager replace contact header in SIP invite

[ajshetty]

My scenario: CM connected to Session Manager to Shortel
CM---- Session Manager---- Shortel

The CM sending call to Session Manager with contact header as Cmext@cmipaddress. The Session Manager can replace destination host URI and Source URI but sends the same contact header and doesn't replace it with its ip address or domain name.
The Shortel when it receives the Invite its looks at contact header and decides that the calling party is CM and not session manager. It cannot route the call since its trunk group has Session Manager IP address and not CM ip address. The other way with call from Shortel to Session manager to CM works fine with only session manager IP address.

We can make it work when we add two trunks on Shortel one with Cm IP address and one with Session Manager address.
Question: Can we modify contact header to Session manager IP address or domain name so that Shortel doesnot see CM address. This is required becuase if we have multiple CM behind Session Manager we cannot keep having so many trunks on one shortel system.
I know SBC can do it can Session Manager do this...?