Open your Gmail account and compose your message and save in draft
Now open this Google sheet and choose the Initialize option under the Email Tracker menu
Now you’ll have to authorize the sheet to send your Gmail messages.
Once the script is authorized, choose Email Tracker -> Send Mail, select your Gmail draft from the drop-down, enter your Google Analytics Profile ID* and hit the Send button. Your mail will be delivered to the recipient.
Now open Google analytic and find Events under the Standard Reports group
Original Source: http://www.labnol.org/