Outlook 2003 and Exchange 2000

[reverendo]

I have a users with Outlook 2003 and they need to conect to Exchange 2000, this had worked fine some days ago, but we changed the Server behind a firewall and this users was unable to connect to exchange server, we have another users with Outlook 2000 and they can connect without problems. We checked permisions on firewall and all is ok (we don't see rejects for this users).

I read about outlook 2003 and the new features i can see is that this support RPC over HTTP this feature can affect this users??

Thanks in advance

PD The server and client both are using Windows 2000