Exchange connection to remote sites

Posted on 2006-11-15
Last Modified: 2008-03-10
I have an exchange server at one location and have 3 remote sites.  There are DC's at all sites and are setup as Global Catalogs.  When I setup an email for new users, OWA works but configuring Outlook I cannot connect the the exchange server.  It tells me that the server is not online or not responding.  They can ping the exchange server, they can even open shared files on the exchange server.  The remote sites are connected with a T1 connection to the main office.  What port does Outlook use to connect to an Exchange server.  I was thinking it might be with the router not letting a certain packets in due to a port not opened or configured?
Question by:infranetsupport
  • 5

Expert Comment

ID: 17949510
It is probably port 135

Expert Comment

ID: 17949518
forward https to an external ip of the main office to the exchange server in your firewall/router and configure the exchange server so that it accepts https connections.

see for client configuration

see for configuring your exchange server

It can be done without https, but then i would recommend setting up a vpn between the offices (if not already implemented)

If you do have an vpn, you will have to open up quite some ports if the traffic tunneld trough the vpn between the 2 locations is filtered.

Expert Comment

ID: 17949533
>Both Microsoft Outlook and Microsoft Exchange use the remote procedure call (RPC) >protocol to communicate. When an Exchange server starts, each of its services are >dynamically assigned to a port. The port number that each Exchange server listens >on can change every time that the Exchange server starts. When an Exchange server >starts, it registers itself with the End Pont Mapper, and prompts the End Pont Mapper >to assign it a port number.

>When Outlook starts, it must determine the port where the TCP/IP end-point on the >Exchange server has been assigned. To find the port number that Outlook must >communicate with, Outlook contacts the Exchange server's End Pont Mapper that >tracks what service is listening on what port. The End Pont Mapper always listens on >port 135.

as stated above, it uses a lot of ports, not just port 135. unless all unprivileged ports are already open, opening port 135 will probably not solve your problem.
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Expert Comment

ID: 17949562
for a more complete list of ports and things to do, see "Preparing Exchange Server 2003 for OWA" at

It also describes a way to limit the amount of ports used.

Accepted Solution

dlangr earned 500 total points
ID: 17950047
in one of my previous posts i said:

forward https to an external ip of the main office to the exchange server in your firewall/router and configure the exchange server so that it accepts https connections.

This was written down a bit to hasty, what i meant is:

In your firewall, forward https of an external ip (at the main office) to the internal exchange server and configure the exchange server so that it accepts https connections.

Expert Comment

ID: 18327487
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