Trying to connect Outlook 2003 from WAN to Exchange 2010 gets credentials box

We have just finished migrated all of our users from Exchange 2003 to Exchange 2010.  We have three sites, each with a 2008 R2 DC, propagating from our corporate site, where the Exchange server is.

After we finished the migration I had a consultant come in and decommission the Exchange 2003 server.  Since that has happened, I have several users in the two sites not in our corporate office that now cannot log onto their e-mail.  When they do try, or when you try to create a new Outlook profile on one of their machines, Outlook starts popping up a logon screen looking for credentials to log onto the mail server.  No matter what credentials you enter or how many times, it just keeps popping up.

Each site has it's own IP scheme, and two of the sites are connected to the corporate site by a managed VPN service.  I can ping the email server by name from the client machine, I can also do an NSLookup.

If I try to do a ping or NSLookup from the domain controller in that remote site, it uses the IPv6 address of APPMAIL first and the ping fails, while the NSLOOKUP shows the IPv6 address then then the IPv4 address.  I added the IPv4 address for the mail server to the LMHOSTS file and now you can ping from the DC, but NSLOOKUP still shows IPV6 address first.

IPv6 is not enabled on the W2008 DC in the remote site.

I'm at a loss, and I'm not hearing back from my consultant at the moment.
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andersonpowerConnect With a Mentor Author Commented:
It turned out that the DC for this site had tombstoned, which is what was causing all the problems.
Randy DownsOWNERCommented:
You could try uninstalling Outlook & reinstalling on the problem machines. I'd also check to see if they happen to have static ips. If they get their ip from DHCP then they are more likely to get current DNS info on your mail servers.
Naushad shaikhIT Consultant - Messaging SupportCommented:
Configure Outlook 2003 in cached mode to connect by using RPC/HTTP with basic authentication.

Make sure that you configure Outlook 2003 to try HTTP only after Outlook 2003 uses TCP/IP. To do this, follow these steps:1. Start Outlook 2003.
2. On the Tools menu, click E-mail Accounts.
3. Click View or change existing e-mail
accounts, and then click Next.
4. Click the Exchange Server e-mail account,
and then click Change.
5. Click More Settings, and then click the
Connection tab.
6. In the Exchange over the Internet area,
click to select the Connect to my Exchange
mailbox using HTTP check box, and then
click Exchange Proxy Settings.
7. Verify that the On slow networks, connect
using HTTP first, then connect using
TCP/IP, check box is not selected.
8. In the Proxy authentication settings area,
click Basic Authentication in the Use this
authentication when connecting to my proxy
server for Exchange box.
9. Click OK two times.
10. Quit Outlook 2003.
11. Make sure that you are connected to the
network. Then, start Outlook 2003.
12. Wait for Outlook 2003 to connect to the
Exchange server. Verify that the
connection is a TCP/IP connection. To do
this, follow these steps:a. Press and
hold CTRL, right-click the Outlook icon
in the notification area, and then click
Connection Status.
b. Verify that the Conn column displays

13. Put the computer on standby.
14. Resume the computer from standby. Then,
wait for about one minute.
15. You are prompted for your user
16. Click Cancel.

This feature requires you to be using a Microsoft Exchange Server e-mail account in Cached Exchange Mode.
Cached Exchange Mode provides you with a better experience when you use a Microsoft Exchange Server e-mail account. A copy of your mailbox is stored on your computer. This copy provides quick access to your data and is frequently updated with the mail server.

If you work offline, whether by choice or due to a connection problem, your data is still available to you instantly wherever you are. If a connection from your computer to the computer running Exchange server isn't available, Outlook switches to Trying to connect or Disconnected. If the connection is restored, Microsoft Outlook automatically switches back to Connected or Connected (Headers). Any changes you make while a connection to the server isn't available are synchronized automatically when a connection is available. You can continue to work while changes are synchronized
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andersonpowerAuthor Commented:
I flushed the DNS on the client machine and reinstalled and am still not able to connect to the Exchange server without getting a request for credentials.  If I try putting the IP of the Exchange 2010 server instead of the server name or FQDN, I get the message "The action could not be completed.  The connection to the Microsoft Exchange Server is unavailable.  Outlook must be online or connected to complete this action."

I can't switch to HTTP without having the Exchange account already set up.  We always use cached mode here.
Outlook 2003 by default does not encrypt communication between itself and the Exchange server.  Exchange 2010 by default requires encrypted communication with Outlook.  Try changing either the server to not require encryption, or set up Outlook 2003 to use encryption.

See this:
andersonpowerAuthor Commented:
Everyone already had encryption enabled, since they had already been migrated to 2010.

It appears it might be an AD issue, with DNS not replicating properly.
andersonpowerAuthor Commented:
Problem turned out to be unrelated to Outlook and Exchange.
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