Hi I had some queries regarding Exchange communication that I was hoping someone could help with; i) In Exchange 2003, I understand that Outlook > Exchange communications is via MAPI. Does this have a specific port? Is RPC involved in this, i.e is it MAPI over RPC, or just MAPI? ii) In Exchange 2007, I understnad that Outlook > Exchange communication is MAPI over RPC. How is this different from Exchange 2003 and what port does this use? iii) How is Exchange 2003 > Exchange 2003 communication (i.e sending mails), what port is used? Is it SMTP? iv) How is Exchange 2007 > Exchange 2007 communication? What port is used? v) How does Exchange 2007 communicate with Exchange 2003? Hope someone can help!

Hi Joe, I. MAPI uses Remote Procedure Calls (RPC) to communicate with the Exchange server. Port 135 for RPC must be available. RPC connections made from Outlook to the Exchange server will first contact the RPC endpoint mapper (Port TCP 135) to request information on the port mappings of the various endpoints required. The Outlook client then tries to make connections to the Exchange server directly by using these endpoint ports. Messaging Application Programming Interface (MAPI) http://msdn.microsoft.com/en-us/library/aa142548(EXCHG.65).aspx Service overview and network port requirements for the Windows Server system http://support.microsoft.com/kb/832017 II. In Exchange 2007, Outlook connects Exchange using the same mechanism as its in Exchange 2003. III. Exchange 2003 uses SMTP(port 25) for sending mail to each other. If you use OWA to access your mailbox, the front-end server will use HTTP to communicate with Back-end server. IV. Please download Exchange Server 2007 Component Architecture, its a picture, you could get the answer. http://www.microsoft.com/downloads/details.aspx?familyid=FDCDF6E5-DE47-4B58-8086-282101BCDDE9&displaylang=en V. Message routing between Exchange 2003 and Exchange 2007 use SMTP. Message Routing in a Coexistence Environment http://technet.microsoft.com/en-us/library/bb125223.aspx Hope this helps. Thanks, Elvis