We are independent & ad-supported. We may earn a commission for purchases made through our links.
Advertiser Disclosure
Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.
How We Make Money
We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently of our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.

What Is an SMTP Relay?

By Eugene P.
Updated May 16, 2024
Our promise to you
EasyTechJunkie is dedicated to creating trustworthy, high-quality content that always prioritizes transparency, integrity, and inclusivity above all else. Our ensure that our content creation and review process includes rigorous fact-checking, evidence-based, and continual updates to ensure accuracy and reliability.

Our Promise to you

Founded in 2002, our company has been a trusted resource for readers seeking informative and engaging content. Our dedication to quality remains unwavering—and will never change. We follow a strict editorial policy, ensuring that our content is authored by highly qualified professionals and edited by subject matter experts. This guarantees that everything we publish is objective, accurate, and trustworthy.

Over the years, we've refined our approach to cover a wide range of topics, providing readers with reliable and practical advice to enhance their knowledge and skills. That's why millions of readers turn to us each year. Join us in celebrating the joy of learning, guided by standards you can trust.

Editorial Standards

At EasyTechJunkie, we are committed to creating content that you can trust. Our editorial process is designed to ensure that every piece of content we publish is accurate, reliable, and informative.

Our team of experienced writers and editors follows a strict set of guidelines to ensure the highest quality content. We conduct thorough research, fact-check all information, and rely on credible sources to back up our claims. Our content is reviewed by subject-matter experts to ensure accuracy and clarity.

We believe in transparency and maintain editorial independence from our advertisers. Our team does not receive direct compensation from advertisers, allowing us to create unbiased content that prioritizes your interests.

A simple mail transfer protocol (SMTP) relay is a computer that is connected to the Internet and is running software that allows it to act as an SMTP server with the intention of directing incoming and outgoing electronic mail (email) to a specific destination online. An SMTP relay server is capable of accepting emails from a remote source and either delivering the emails internally, if the destination is the server itself, or forwarding those emails to other SMTP servers as needed. Additionally, such a relay can be configured in different ways to help prevent malicious emails or junk emails from being processed. There are two primary types of SMTP relay servers, with the first being an open relay by which any computer anywhere in the world can connect and send mail through the server. The second type is an authenticated relay, through which any system that connects to the SMTP relay must provide at least one valid username and password combination, though multiple usernames and passwords also might be required for each operation.

When an email message is composed and sent by a user, the message generally is passed through an SMTP server to reach the recipient. If one SMTP server contacts another SMTP server and transfers an email to it, then the SMTP server that receives the email is known as an SMTP relay, because it is relaying the email. The relay does not have to be the target server and can act as a gateway or intermediary step between the source server and the destination server. Should the relay be the target server, the email messages that are received can be passed to local software so they can be retrieved by client programs as needed.

Many SMTP relay servers use authentication to sort out what incoming mail traffic should be processed and what messages should be rejected and left for other servers to process. Frequently, an SMTP relay will only serve incoming or outgoing messages that have some relation to the Internet domain to which it is connected. This prevents anonymous or random users from using the server to send emails that could be harmful or unwelcomed. If no authentication is required, then the SMTP relay simply will process all incoming messages as best it can.

In some situations, an SMTP relay server can be hosted on a dedicated machine. This has the benefit of isolating the server from the rest of a larger network. It also allows one relay to act as a front-end filter, removing harmful emails or stripping messages of their attachments before passing them to other SMTP relays for actual processing.

EasyTechJunkie is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Discussion Comments
EasyTechJunkie, in your inbox

Our latest articles, guides, and more, delivered daily.

EasyTechJunkie, in your inbox

Our latest articles, guides, and more, delivered daily.