Please note you need to follow these steps for each QuickBooks file you want to email from.
Open QuickBooks File
Go To [Edit] - [Preferences]
Select "Send Forms" on the left panel
Click "My Preferences" tab
Choose "Web Mail" and click "Add"
Enter your Email Address, and indicate that it is a "GMail" account.
Log in to your email account in the Browser window it opens
Grant Acceess to QuickBooks to use your Email.
Close Browser Window
Click OK in the QB Preferences window