Create a legacy Exchange host name


Estimated time to complete: 5 minutes

You need to create a legacy domain name system (DNS) host name so your legacy Exchange 2007 environment and Exchange 2013 can coexist. For example, if your domain name is currently, you're likely using a host name of or for external client access to Exchange. During coexistence, we recommend creating and using, for example, a host name of You'll associate the legacy host name with your existing Exchange 2007 server and associate your current host name (for example, with your Exchange 2013 Client Access server. Your end users will not see or use the legacy host name. It will be used by Autodiscover and Client Access servers when redirecting legacy users to a legacy server.

Client connections, including Exchange ActiveSync, Outlook Web App, POP3, and IMAP4, will be proxied or redirected depending on the protocol being used. After the legacy host name has been configured, users will be able to access their mailbox regardless of whether it's on Exchange 2007 or Exchange 2013. If you're upgrading from Exchange 2007 to Exchange 2013, the following will happen:

  • ActiveSync and Outlook Anywhere connections will be proxied from Exchange 2013 to Exchange 2007.

  • Outlook Web App and Exchange Web Services (EWS) connections will be redirected from Exchange 2013 to Exchange 2007.

How do I do this?

You need to create a public DNS record for the host name to point to the external IP address of your Exchange 2007 server. The following is an example of the DNS record that you'd create with your public DNS provider, such as GoDaddy.

You also need to configure the ExternalURL properties of your Exchange 2007 Outlook Web App and EWS virtual directories to use the new legacy URL. This is done in a step later on in the checklist.


You might need to make changes to your firewall to support this new legacy host name. You might need to add new firewall rules, add an external IP address for your Exchange 2007 server, or make other configuration changes. If your organization has a network management group, a security review process, or change management process, you may need to request permission to perform these changes or have someone else make them for you.

Host name DNS record type Value


How do I know this worked?

To verify that you've successfully configured your public DNS records, do the following:

  1. Open a command prompt and run nslookup.exe.

  2. Change to a DNS server that can query your public DNS zone.

  3. In nslookup, look up the record for the host name you created. Verify that the IP address that's returned matches the external IP address of your Exchange 2007 server.

Having problems? Ask for help in the Exchange forums. Visit the forums at Exchange Server, Exchange Online, or Exchange Online Protection.