Communicating across a DMZ

If you can't ping the server from these 5 computers, you most likely have either a routing or an access list problem and the answer is likely to be found in the configuration of whatever device sets off the DMZ (PIX firewall, etc.) or in the workstation configuration itself.

I think I would start by doing an 'ipconfig /all' and compare the settings of the computers that work versus those that don't and see if anything looks funny.

Then I would do a 'tracert' and see if the path is what I think it should be.

I'd also spend some time with the firewall configuration and look, in particular, for any access lists, weirdly subnetted routing statements, authentication parameters, etc.

Also, I'd be curious to know what you mean by "I can see the server on the network". Do you mean it appears in Network Neighborhood?

Finally, remember that Outlook communicating with Exchange uses remote procedure calls over dynamic ports so there are special considerations for operating througha firewall although I can't offer an explanation why that would affect some machines and not others.

If you can re-post with additional information about your physical setup (type of firewall, type of LAN), I may be able to point you in a more productive direction for solving this problem.

paul