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Ports that Outlook 2003 use to communicate

Hi there

We would like to segregate a section of our LAN. We would like to configure a Firewall to only allow access to certain ports on our Exchange 2003 so that users in this segment are able to connect with their outlook and use its full functionality.

My question is what ports are necessary for outlook to be able to function correctly??

I have found the following articles, but they are more related to what ports Exchange 2000 / 2003 use :


Any help would be appreciated.

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1 Solution

outlook 2003 used Mapi to comminicate with exchange server, the ports used when outlook connects to an exchange server are RPC assigned ports. You could use rpc over http to tunnel through the firewall , also cisco pix 7.0 has an inspect command for passing RPC.
(I have read recently that it is possible to tie down RPC assigned ports for certain services )

Why do you want to place a firewall between your outlook clients and exchange? Depending on answer, it might be better to use a frontend exchange -> firewall -> backend exchange server -> outlook client solution?
As hinted above, if you want to lock things down then use RPC over HTTPS. Then you are looking at a single port - 443. Just make sure everything resolves correctly.

Although I am not a fan of internal firewalls blocking access to Exchange. In those scenarios I prefer Exchange and a domain controller to be placed somewhere where everyone has full access (like a DMZ, but with all ports open).

jafar54Author Commented:
ok i get that reasoning to use RPC over HTTPS...... but say you didn't wanna go that way. Say you are using a unintelligent dumb firewall where you need to specify all the ports required..... ie. the FW is not application aware or anything.

Now you have clients that are using Outlook 2003 with cache mode enabled.... .your Exchange server is setup normally, no fancy config, straight out the box. You also have a stock standard front end server provisioning OWA and OMA.

What ports would you need to open? Or is the message that the easiest and simplest way to do is to use the single port approach with RCP over HTTPS?


When the port ares assigned by RPC, they are assigned in a dynamic fashion each time you restart the service, one time they could be 12345 etc and then on the next restart 54311 etc.   If you are using a dumb firewall the the best solution is to use RPC over HTTPS.

As I mentioned in a previous post, you can stop the dynamic nature of RPC (Still really advise using RPC over HTTPS).



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