Exchange 2010 Default Email Address Policy

Ok, I have a brand new install of Exchange 2010.  It is installed on a Windows 2008 R2 DC (not my idea - I tried to talk the company into seperate Exchange servers) and was NOT migrated from any other Exchange implementation.  It's a straight install of E2K10 Standard.  Now, I want to edit the Default email address that every users gets - you know, the way you USED to be able to without any problems - but I keep getting an error that you cannot do this to the Default Policy.  I have tried everything that I can find on this subject to get the ability to do this but so far so bad.  The domain was named something other than the email addresses that will be used and during the installation I told Exchange that the organization was the domain name.  I thought I was being asked what domain Exchange was going to be working the email organization for.  Now, I am having the problem listed above.  I thought I would be able to simply edit the default email address and everyone will get the correct appended address to their account when they get an email address created for them.  I know this has been asked before and I aplogize for asking again but so far everything I have found will not allow me to change the address.  I don't want to change how the policy works just the email address you get when you're created.  Since I can't edit the email address, at this point  I am wondering if this is a permissions issue.  Can someone please tell me what kind of flaming hoops and rickety ladders I have to go through just so I can edit the email address so it'll stick?  I'm going to keep looking at this for the moment but I am hoping someone can send me in the right direction since I've been looking at this for a little while now.

     Thanks to anyone that responds and please shoot me in the right direction -
                   Jon