Gmail as Relay in PostFix

1. Go to the following link: Manage your account access and security settings . Scroll down to “Password & sign-in method” and click 2-Step Verification. Then enable it.
2. Click the following link to Generate an App password for Postfix.
3. Click Select app and choose Other (custom name) from the drop-down menu. Enter “Postfix” and click Generate . Save the password.
4. Log in to Plesk server using SSH.
5. Open or create the /etc/postfix/sasl/sasl_passwd file and add the SMTP Host, username, and password information:
   [smtp.gmail.com]:587 username@gmail.com:password
   Use the password from the 3d step.
6. Create the hash db file for Postfix by running the postmap command:
   # postmap /etc/postfix/sasl/sasl_passwd
7. Run the following commands to change the ownership to root and update the permissions for the two files:
   # sudo chown root:root /etc/postfix/sasl/sasl_passwd /etc/postfix/sasl/sasl_passwd.db
   # sudo chmod 0600 /etc/postfix/sasl/sasl_passwd /etc/postfix/sasl/sasl_passwd.db
8. Find and modify relayhost in /etc/postfix/main.cf to match the following example:
   relayhost = [smtp.gmail.com]:587
   Set this in the end of /etc/postfix/main.cf file:
   # 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
9. Restart Postfix:
   # service postfix restart