Cisco Firewall :: Exchange Direct Push / ASA 5540 / Barracuda?

I have the following scenario.
 
                            INET
                      (205.50.50.1)
                              |
                              |
                      (205.50.50.2)
                 [CISCO ASA 5540]
                       (10.10.10.1)
                              |
                              |
                             + ---------------------------------------------+
                      (10.10.10.2)                              (10.10.10.3)
                    [BARRACUDA]                         [Exchange SRV]
 
 Mail Domain:            mail.domain.com (205.50.50.50)
 
Ok so the mail flows to the Barracuda using a static 1:1 NAT configuration and then gets delivered from the Barracuda to the Exchange server.  I want to implement active sync (Direct Push) for Windows mobile devices.  They need to communicate with mail.domain.com over port 443.  The problem is I want mail to continue to flow to the Barracuda, but direct Direct Push traffic to the Exchange server.I cnow I can't implement two 1:1 NAT mappings from the same external hostname to 2 different servers.