Outlook could not log on. Unable to authenticate with EX Server

[Guest]

Details:

I am using Outlook 2003 to connect to Exchanger Server 2003
OS: WinXP
I connect through a VPN to the exchange server. I can ping the server using
the computer name without the domain. I can connect to the server and
explore (\\exchangeservername). However, while attempting create a new
exchange email account and verify/authenticate, I get the following error
message (after a long delay/hang):

"Outlook could not log on. Check to make sure you are connected to the
network and are using the proper server and mailbox name. The connection to
the Microsoft Exchange server is unavailable. Outlook must be online or
connected to complete this action.

I have uninstalled and reinstalled Outlook several times, ran the office
2003 repair tool, verified the RPC registry entries are correct, even added
my server IP to the hosts file. Any ideas what else might be wrong???

 

[neo [mvp outlook]]

Start Outlook 2003 with the /rpcdiag switch and see if you are able to get a
connection to a Global Catalog (domain controller).

 

[Guest]

Unable to make the connection. The machine I connect to shows type:referral
so I know my connection is getting to the domain controller. However, from
there, it hangs. Any ideas from this point?

 

[neo [mvp outlook]]

If you haven't done this already, try changing Outlook 2003's authentication
from Kerberos/NTLM to just NTLM. If Outlook was running, you would get at
this setting by r-clicking on outlook today > properties > advanced >
security tab.

 

[Guest]

You're a genius! It worked. Why would that suddenly have caused a problem?
Not a big deal, just curious. I've been racking my brain on this one for
quite some time.

 

[neo [mvp outlook]]

Kerberos authentication is done over UDP. Some VPN solutions will drop UDP
network packets when they go over a certain size. When this happens, you
can't get authenticated/connected.

/neo