Change Primary Email Address in Exchange 2010

I have an Exchange user that had special requested an address and it was approved by management.  Now they want me to change it.  The example is as follows:

John Smith requested email as:
The standard naming for the company is first initial last name @ so he normally would have been setup as  
Knowing that users might address their emails based on the companies standard practice, I added to his Exchange email addresses tab so the would catch any misguided emails.
Now, management has come back and said "No, we want you to change him to the standard naming.
The user logs on to the domain (OWA) as john.  How can I easily reverse these settings without interruption to his account?  Can I still have him logon to his account as john or do I need to change his logon parameters to jsmith as well?  In the properties of his profile (on Exchange) and cant set the secondary account to primary.
Any suggestions please?
cobmoIT ManagerAsked:
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in ADUC you can change the logon to windows. Navigate to his name in Active Directory and go to properties and change the "user logon name"

In Exchange 2010 MMC if you navigate to Receipient Configurations and mailboxes and go the users properties then go to the email address tab and click on what should be the right email address and click on "set as reply"

let me know if this works.

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Will SzymkowskiSenior Solution ArchitectCommented:
You login to the domain (UPN or sAMAccountName) is different than your Email Address Policy. All you need to do is open the EMC Fine the user click on the emailaddress tab Click the check box (lower left corner) Update Email based on email address policy. This will force his account to use the email address policy. You can then remove any other Alias that you have as secondary's.

This will not affect his account for login or Exchange.

cobmoIT ManagerAuthor Commented:
For whatever reason there is no email policy set.  We have only about 125 users so not much activity.  Manually type it is not an issue.

I changed his logon to jsmith in ADUC and his alias on his properties page in Exchange.  I see now that it automatically highlighted the jsmith account under email addresses.  However, the Set Reply is grayed out Im assuming bc there is no active Email Policy. The policy in place was legacy from who knows when.

His password should be the same.  He just needs to change his logon name for OWA and reconfigure his phone account for Active Sync using the new credentials.  Mail will still come into but guess his replies will go out
No for the set reply you have to uncheck the setting that is there underneath. I forgot the setting that is on that dialog box that has the set reply option. Once you uncheck the option to set as reply is no longer greyed out.
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