Ask the Expert

DNS problem preventing branch office from connecting to Exchange server

We have Exchange 5.5 SP4 on a Windows 2000 SP4 server. The clients used Office 2000 SP3 (Outlook) on Windows XP Professional for workstations. We have two offices under the same domain connected via a VPN with the same ISP and multiple smaller sites set up as groups; these are connected via VPNs, but with other ISPs.

After changing our DNS configuration, which is external via our ISP, the users in our offices can use Outlook with no problem. But the users in the smaller sites can no longer connect to the Exchange server. Presently, they use an internal Outlook Web Access 5.5, but this is far from ideal. Do you have any ideas?

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It sounds like a DNS issue. Check your DNS server for duplicate names that may be causing the problems. Can you ping the FQDN server name from the remote location? Can you ping the IP address of the server from the remote location?

Add an entry for the mail server to hosts and lmhosts under C:\windows\system32\drivers\etc and test the connectivity.

Example for Hosts:

Example for Lmhosts: yourmailserver #PRE #DOM domainname
C:\nbtstat –R
C:\nbtstat –C (check the server name configuration)

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Related information from

  • Tutorial: A primer on DNS and MX records
  • Free Download: Nslookup
  • Tip: Free script for importing/exporting DNS information
  • Reference Center: DNS tips and resources

  • This was first published in February 2006

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