I wanted to send email reports from my computers. For that, the easiest is to create additional Gmail account (so your private email is safe) and set-up SSMTP:
sudo apt-get install ssmtp mailutils
Configure SSMTP: comment all lines in /etc/ssmtp/ssmtp.conf and add at the end (replacing HOSTNAME/USER/PASSWORD with your info):
root=postmaster
hostname=HOSTNAME
mailhub=smtp.gmail.com:465
AuthUser=USER@gmail.com
AuthPass=PASSWORD
FromLineOverride=YES
UseTLS=YES
Then, allow access from less secure apps to created Gmail account and enable one-time sign-in for new app without captcha. It’s strongly recommended not to use your private account for that purpose!
And send emails:
echo "email body" | mail -s "Test email from "`hostname` SOMEUSER@gmail.com
Voilà!
Note, this works perfectly fine in Ubuntu, as well as in Raspberry Pi.
On 30 May 2022 less secure passwords were disabled. But you can use app specific passwords after you enable two-factor authentication https://myaccount.google.com/u/1/apppasswords