How to Set Up SMTP Relay Without Authentication

Explore how to set up smtp relay without authentication can improve your email deliverability and marketing efficiency.

The setting of an SMTP relay without any form of authentication is good for scenarios, such as scanning devices like scanners, printers, and even IoTs that lack complex authentication mechanism support. But then again, using it this way must be handled with utmost care as this could provide avenues to those with malicious intentions. For the guide, I will help walk you through the way to set up an SMTP relay with no authentication involved, being very keen on the best practices in securing your relay.

SMTP (Simple Mail Transfer Protocol) relay provides a way to route messages through a server to their destination email provider. A typical SMTP relay requires some form of authentication to ensure only authorized users or devices are allowed to send email from it. However, some devices do not support authentication. In such cases, this relay needs to be made accessible without authentication in particular situations.

When to Use SMTP Relay Without Authentication

The SMTP relays without authentication best are on internal networks and mostly use them for email relay by the devices or application lacking these modern authentication methods. These have a few legit use-cases; such ones include:

Use cases involving sending documents from a printer or scanner.

Systems send automatic alerts with being the embedded systems.

Those that will not support login of SMPT secure use

Note: This isn’t usable over the internet nor good for sending email spams as it will get a hold of other individuals.

Setting Up SMTP Relay Without Authentication

If you do not already have an SMTP server, you can set one up using tools such as:

Choose the server software best suited for your operating system and follow the installation instructions specific to that software.

Step 2: Configure the SMTP Server for Unauthenticated Relay

Since you’re bypassing authentication, it’s essential to limit access to trusted IP addresses within your network. Only devices within your internal network should be allowed to use this relay.

Postfix : Open main.cf and configure the mynetworks directive to specify allowed IP ranges.