April 26, 2013
Outlook version 14.3.2 has a known bug where it will be unable to email groups with a Microsoft Exchange account. Microsoft has announced that it will release a fix in May, but that the current work around is to act as if you were going to email the group normally, putting it in the To... section and then clicking on the little icon to the left of the group to expand it (it will put everyone individually into the To...section).
If this doesn't work, it may work by using the Bcc section instead.
The only other solution is to uninstall and reinstall Office 2011 and not allow it to update to this version.