If you try to modify the recipient filter of the default Global Address List in Exchange Server 2010 you will receive an error message:

You can’t peform this operation on default global address list “Default Global Address List”.

The recipient filter of the default Global Address List can be modified once during conversion from Exchange 2003 but not after that.  If you want to change the default Global Address List recipient filter after that you must either:

• Create a new Global Address List with the desired recipient filter
• Temporarily modify the Global Address List so that it isn’t the default

For the second option you can refer back to my earlier post on fixing  the issue where there is no default Global Address List in the organization.  This is determined by the msExchRecipientFilterFlags attribute of the object.

Simply use ADSIEdit.msc to modify the attribute from 3 to 0, apply the change to the Global Address List recipient filter, then return to ADSIEdit.msc and set the flag back to 3.  For more detailed instructions check out my previous post.