Postfix Install

The below steps will setup Postfix with Gmail SMTP to send emails. Gmail can be swapped out for your email provider of choice. In this tutorial we are using Ubuntu for the setup.

Firstly, update the system packages

Update packages

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

Install Postfix package

sudo apt-get install postfix

Select the Internet Site option

Generate Gmail App Password

Follow the guide located here to setup an App Password for your Gmail account

Setup SASL

Create a SASL Auth file for Postfix

vi /etc/postfix/sasl/sasl_credentials

Add the Gmail app password to the file

[smtp.gmail.com]:587 exampleuser@gmail.com:aodrkojoafdnyqyl

Create Hash Database file

Run the following to create the file

sudo postmap /etc/postfix/sasl/sasl_credentials

This will create a new file /etc/postfix/sasl/sasl_credentials.db

Change permissions on database file

In order to protect the credentials of the file run the following

sudo chown root:root /etc/postfix/sasl/sasl_credentials /etc/postfix/sasl/sasl_credentials.db 
sudo chmod 0600 /etc/postfix/sasl/sasl_credentials /etc/postfix/sasl/sasl_credentials.db

Set postfix relay & SASL config

Modify the relay config in the /etc/postfix/main.cf

mydestination = $myhostname, localhost, localhost.localdomain 
relayhost = [smtp.gmail.com]:587 
mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128

Add the following to the bottom of /etc/postfix/main.cf

smtp_sasl_auth_enable = yes 
smtp_sasl_security_options = noanonymous 
smtp_sasl_password_maps = hash:/etc/postfix/sasl/sasl_credentials
smtp_tls_security_level = encrypt 
smtp_tls_CAfile = /etc/ssl/certs/ca-certificates.crt

Restart postfix

sudo systemctl restart postfix

Test email

To test the postfix config using sendmail do the following

sendmail you@youremailaddress.com 
To: you@youremailaddress.com
Subject: Test Postfix Email
This is a test mail to test Postfix