Add additional SMTP address to all users in Exchange 2010 SP1

I am trying to find a script that will allow me to add an additional email address to everyone in the company in the format of:

firstname.lastname@domain.com

I do not want this to be the default address (so email policy won't work), and I don't want to lose the addresses already assigned to the account.

I have found a lot of questions similar to this one in the forums, and one that seems to be exactly what I want, but it might be dated as it isn't working when I save it as addaddress.ps1 and then run it from the Exchange Management Shell. 

The script I found that is supposed to to exactly what I'm looking for was found in this post:

http://social.technet.microsoft.com/Forums/en-US/bd96d066-fd45-4395-bfb5-ab907396d8a3/exchange-2007-ps-command-to-add-firstnamelastnamemydomaincom-smtp-address?forum=exchangesvrgenerallegacy

It is as follows:

I'm running Exchange 2010 Sp1

I tried posting this over in the Exchange forum, but someone suggested that I post it over here instead.  On that forum they kept directing me to Email Address policy (which will change the default email address).