Exchange 2007

Hello Everyone:
Can’t seem to remember if there was a solution to this problem I am having.

I have a single user who already has an exchange mailbox. This user needs a second mailbox created. Is this even possible, and how can it be completed.

On the AD side, our naming format firstname.lastname@domainname.com
This user requires a single name like
john@domainname.com.

Can this be accomplished without creating a group mailbox?

Appreciate any feedback on how to accomplish this.