As we know by default the Display Name of Exchange Mailboxes(Exchange Server 2007 SP2) is in the format of “Firstname Lastname”. I want to change this for the couple of existing mailboxes to “Lastname, Firstname” for one my customer – he preferred non-development stuff!!

I tried to do the same using the Exchange Management Shell, which fits for my requirement:
> Get-Mailbox “User Name” | Get-User | ?{ $_.Lastname -ne $null } | %{ $dispName=$_.LastName + “, ” + $_.FirstName ; set-mailbox $_.SamAccountName -Displayname $dispName }

In case you want to revert back to the format “Firstname Lastname”, here’s the command for that.
> Get-Mailbox “User Name” | Get-User | ?{ $_.Lastname -ne $null } | %{ $dispName=$_.FirstName + ” ” + $_.LastName ; set-mailbox $_.SamAccountName -Displayname $dispName }

You can try this out…