HOW-TO: Quickly Setup Postfix with Gmail

Overview

When Two-Factor Authentication (2FA) is enabled, Gmail is preconfigured to refuse connections from applications like Postfix that don’t provide the second step of authentication. While this is an important security measure that is designed to restrict unauthorized users from accessing your account, it hinders sending mail through some SMTP clients as you’re doing here. Follow these steps to configure Gmail to create a Postfix-specific password:

1. Log in to your email, then click the following link: Manage your account access and security settings. Scroll down to “Password & sign-in method” and click 2-Step Verification. You may be asked for your password and a verification code before continuing. Ensure that 2-Step Verification is enabled.

1. Click the following link to an App password for Postfix:

Step-By-Step

sudo apt-get update && sudo apt-get upgrade

sudo apt-get install libsasl2-modules postfix

sudo vi /etc/postfix/sasl/sasl_passwd
    [smtp.gmail.com]:587 [email protected]:OneTimePassword
    
sudo postmap /etc/postfix/sasl/sasl_passwd

sudo vi /etc/postfix/main.cf
     relayhost = [smtp.gmail.com]:587
     # Enable SASL authentication
     smtp_sasl_auth_enable = yes
     # Disallow methods that allow anonymous authentication
     smtp_sasl_security_options = noanonymous
     # Location of sasl_passwd
     smtp_sasl_password_maps = hash:/etc/postfix/sasl/sasl_passwd
     # Enable STARTTLS encryption
     smtp_tls_security_level = encrypt
     # Location of CA certificates
     smtp_tls_CAfile = /etc/ssl/certs/ca-certificates.crt
        
sudo systemctl restart postfix

mail -s "Hello World" [email protected] < /dev/null

# or mutt
sudo apt install mutt
mutt -s "Hello World" [email protected] < /dev/null