How to Postfix smtp relay

Explore how postfix smtp relay can improve your email deliverability and marketing efficiency.

Installing a Postfix SMTP relay will only be useful in the case of controlling your email delivery, but most importantly, it’ll help you route mail out going through another server. Let’s walk you through how to configure Postfix as an SMTP relay step by step. To conclude this guide, you’ll quite clearly understand how to set up, test, and secure your Postfix relay server. Let’s begin now.

Postfix is an open-source mail transfer agent which routes and delivers email; it’s very popular for security, ease of use, and flexibility. Using Postfix as an SMTP relay will forward your emails to another SMTP server to be delivered.

Before starting, make sure you meet the following prerequisites:

A server having Postfix installed (usually a Linux-based server like Ubuntu or CentOS).

You have either the root or sudo access to the server.

You will need an external SMTP server; otherwise, it can be Gmail, SendGrid, or any local email server.

Basic understanding of command-line operations is also assumed.

If Postfix isn’t already installed, you can install it using your server’s package manager. Here’s how to do it on some popular Linux distributions:

During the installation, you might be prompted to choose a configuration type. Select “Internet Site” , and for the “System mail name,” enter your domain (e.g., example.com ).

Step 2: Configure Postfix as an SMTP Relay

The main configuration file for Postfix is located at /etc/postfix/main.cf . You’ll need to edit this file to set up the relay host.

2- Find the line that starts with relayhost = and modify it to point to your relay server.

For example, if you’re using Gmail’s SMTP server:

3- Add or modify the following lines to ensure your Postfix server uses the correct authentication method: