Microsoft Office Communicator (MOC) client connect to Exchange server to retrieve free/busy information when Personal Information Manager (PIM) configure to use Outlook. During this process MOC use HTTPS, RPC and MAPI ports to connect Exchange server, this is the normal behavior of communicator client.

When WAN accelerators used between client site and datacenter, MOC client port requirement to connect Exchange servers is not the same as default behavior.  This doesn’t mean Exchange server listening on different port number. Destinations ports of MOC client connect to Exchange servers with or without WAN accelerators are default MAPI, RPC & HTTPS ports.

What is the WAN accelerators port modification?

WAN accelerators will implement between two different sites which connect on slow link. WAN accelerators will place in both sites to optimize the traffic on slow link between two sites. When WAN accelerators optimize MAPI traffic to make Outlook connection faster it use custom single TCP port (This port can be define I WAN Accelerator) for MAPI traffic. MAPI optimization will affect MOC client also because MOC use MAPI protocol to connect Exchange mailbox server.

How it works?

Exchange server side listening ports will remain same as default. In MOC client side it is visible the destination MAPI ports as MAPI Optimization port configured in local WAN accelerator but in server side WAN accelerators translate this port to default MAPI ports again.