Whenever a company merges with another or changes domain names for some other reason, everyone's e-mail addresses inevitably change, too.
However, simply changing everyone's e-mail address overnight is a bad idea because unless each employee forwards his or her new address to everyone in their address book immediately, it will take time before the new address is universally known. The solution for many companies is to leave the old e-mail addresses active for a short period of time during the transition.
The question remains: How do you assign multiple e-mail addresses to each user and how do you remove one of the addresses once the transition period expires?
It comes down to the DNS configuration
There is more to the answer than just changing a few settings on an Exchange server. What you need to do depends on your network's DNS configuration on the Exchange configuration.
Think about it for a moment. Mail does not arrive in your server's mailboxes by magic. When someone outside of your organization attempts to send you an e-mail message, their machine performs a DNS query to determine the IP address associated with your domain. Specifically, this query involves checking the domain's MX record. The MX record contains your mail server's IP address.
Suppose, for example, that I decided I wanted to give up my brienposey.com e-mail address and use newdomain.com instead. Even if I configured my Exchange Server to associate the newdomain.com domain with my mailboxes, mail sent to Brien@newdomain.com would never arrive unless an MX record was in place on the DNS server that is authoritative over my new domain.
If I wanted to have a transition period when both of my e-mail addresses were valid, I could simply have an MX record associated with brienposey.com and another MX record associated with newdomain.com. Both of these MX records would point to the same mail server. When the transition period was over, I could then just delete the MX record associated with brienposey.com, which would ensure that brienposey.com e-mail addresses were no longer valid for those outside of my organization.
Step 2: Configure your Exchange Server
Configuring the DNS server is only half of the solution. The other half involves configuring the Exchange Server. To do so, open the Exchange System Manager and expand the Recipients container, and then select the Recipient Policy container beneath it. When you do, you will see the organization's recipient policy appear in the console's details pane. Right click on the recipient policy that you want to modify and select the Properties command from the resulting shortcut menu. Windows will then display the recipient policy's properties sheet.
Select the properties sheet's e-Mail Address (Policy) tab and you will see a list of the e-mail addresses that apply to the users in your Exchange organization. Normally, there will be one SMTP address and one X.400 address. There may also be other types of addresses depending on your server's configuration. I will focus on the SMTP address.
To add the new address to the recipient policy, click the New button. When you do, you will see a warning message indicating that the new address will not automatically be synchronized with an Exchange 5.5 directory (if one even exists). Click OK to acknowledge the message and you will now be prompted to select the type of address that you wish to create.
Select the SMTP Address option and click OK. You will now see the SMTP Address Properties sheet. Enter the new address into the Address field in the *@newaddress.com format. Verify that the properties sheet's check box is selected and click OK.
The new address will now be added to the list of the organization's addresses, but it isn't active yet. To activate the new address, select the check box next to it and click OK.
At this point you will see a message asking you if you want to update all of the corresponding recipient e-mail addresses to match the new address format. Click Yes and you are in business.
Final step: Phase out the old address
Now that you have associated multiple addresses with each mailbox, let's look at the process for phasing out the old address. You first need to remove the DNS server's MX record associated with the old address, which prevents your users from receiving any more mail through that address.
Next, return to the recipient policy's properties sheet. Select the new e-mail address and click the Set As Primary button. This will tell Exchange that the new address is the main SMTP address that you want to use. Next, select the old address and click the Remove button. Click OK and you may see the message again asking if you want to update the recipient mailboxes. Click Yes and you are done.
Brien M. Posey, MCSE, is a Microsoft Most Valuable Professional for his work with Windows 2000 Server and IIS. Brien has served as the CIO for a nationwide chain of hospitals and was once in charge of IT security for Fort Knox. As a freelance technical writer he has written for Microsoft, CNET, ZDNet, TechTarget, MSD2D, Relevant Technologies and other technology companies. You can visit Brien's personal Web site at http://www.brienposey.com.
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