Search the Global Address List (GAL) by last name -
Open the Global Address List (GAL) by clicking on the little open book icon on the email tool bar.
Select the "magnifying glass over a book" icon.
In the new window that opens, in the box marked "last name" type the full lastname of the person you would like to find, and click "OK".
A list will appear of all the people whose lastname begins with that.
Select the name of the person you wish to email.
Go to the menu bar and select "File", then select "new message"
An empty new mail message addressed to the selected person will appear for you create and send an email message.