View the original community article here
Last tested: Jul 1, 2019
Simple Mail Transfer Protocol (SMTP) is the universal standard protocol for communication via email. When sending an email from your Looker Google account, you use SMTP. All emails coming from Looker to outside email addresses also use SMTP.
In Looker, you can either use custom SMTP settings so that all email messages come from an account you control, or you can use the default SMTP settings to take advantage of Looker’s email service, without the need for additional configuration. So that, all emails will come from firstname.lastname@example.org.
Custom SMTP is set up in the Admin > SMTP panel.