Configure ssmtp to use the mail Linux command line to send email with gmail

First of all, install the ssmtp package:

bougui@aldebaran ~> sudo apt-get install ssmtp

Then edit the file /etc/ssmtp and just pust that content to the file:

#Debug=YES
root=USER@gmail.com
AuthUser=USER@gmail.com
AuthPass=YOUR_GMAIL_PASSWORD
FromLineOverride=YES
mailhub=smtp.gmail.com:465
UseTLS=YES

Then, a quick test:

bougui@aldebaran ~> echo "This is a test" | mail -s "Test" USER@gmail.com

For sure, just replace USER by your Gmail username, in the configuration file and in the test command line.