SMTP Relay: What Is It and How Does It Work

author image

Written by:Aquibur Rahman


Facebook logo
Linkedin logo
Twitter logo
Whatsapp logo
Pinterest logo
mail logo
copy link

As an email marketer, would you like to limit yourself to sending just a couple of hundred or thousand emails per day by your mailbox providers? No, right?

But unfortunately, many mailbox providers have already set up a sending limit for each account that you can’t cross. This is done to control the ever-growing spam emails that haunt the email world.

But you’re not a spammer, and it feels unfair that you also have to oblige this rule. This is where Simple Mail Transfer Protocol (SMTP) relay and SMTP relay services come to the rescue.

Keep on reading to know all about SMTP relay and how to use it to improve your campaign performance.

Table of contents

What is an SMTP relay?

SMTP relay is a method that helps emails to travel between multiple email servers. This particularly helps email marketers interested in sending batch or automated emails without having to face major deliverability issues.

How does SMTP relay work?

SMTP relay can be a bit confusing, so let’s try to understand with an analogy.

Assume that you want to send a snail mail to your friend in another town. You write your mail, wrap it in an envelope, add the delivery information, and put it in your local postbox office.

Then the postman will pick up your snail mail and deliver it to the appropriate postbox in your friend's town. Finally, your friend will receive your mail.

SMTP relay works similarly. It is the process of sending your mail from one postbox to another. When defined in the words of electronic mails (e-mails), it’s the process of sending emails from one SMTP server to another.

Get the State of Email 2023 Report

150+ email experts share their email tips and secrets

Why do you need SMTP relay services?

First, let’s understand what SMTP relay services are. These are just companies that provide other companies with SMTP relay services.

You may ask, “But why should I go to another company for SMTP services? Can’t I set up my own SMTP server and call it a day?” Good question.

First of all, email marketing is not easy. On the surface, it may seem like you are sending emails to your email list, and subscribers will receive them without any issues.

But in reality, many emails don’t reach users’ inboxes due to deliverability issues caused by your SMTP server. To be able to find and fix those problems, you need to be that tech guy who knows the ins and outs of SMTP servers. But many don’t have or want to build that knowledge for various reasons.

Also Read: Everything You Need to Know About Email Deliverability

This is where an SMTP relay service will take care of your SMTP needs. It’ll ensure that you achieve optimum deliverability rates and keep your IP and domain reputation high.

These services also help you send emails in large volumes and let you be not limited by the limit that mailbox providers have set for their accounts.

How do I find the SMTP server host?

This is one of the commonly asked questions about SMTP relay. So here’s how to do it step-by-step:

  1. Type Windows key + R and hit enter.

  2. Type cmd and hit enter.

  3. Type nslookup and hit enter.

  4. Type set type=MX and hit enter.

  5. Type a domain name and hit enter.

You’ll see the hostnames that are set up for SMTP.


Email marketers would have a hard time without SMTP relay. And without SMTP relay services, many marketers would keep wondering why their email deliverability is so low and how to fix it.

The SMTP protocol is a complex topic to understand, and many marketers have a hard time finding an easy-to-understand guide that’ll teach them everything they need to know. Fortunately, we already have a guide on SMTP you can check out that’ll teach you everything you need to know in an easy-to-understand manner.

What you should do next

Hey there, thanks for reading till the end. Here are 3 ways we can help you grow your business:

  1. Talk to an email expert. Need someone to take your email marketing to the next level? Mailmodo’s experts are here for you. Schedule a 30-minute email consultation. Don’t worry, it’s on the house. Book a meet here.

  2. Send emails that bring higher conversions. Mailmodo is an ESP that helps you to create and send app-like interactive emails with forms, carts, calendars, games, and other widgets for higher conversions. Get started for free.

  3. Get smarter with our email resources. Explore all our knowledge base here and learn about email marketing, marketing strategies, best practices, growth hacks, case studies, templates, and more. Access guides here.

About the author

author profile avatar


Aquibur is the CEO and co-founder of Mailmodo. He's helped various tech companies set up their email marketing infrastructure. His work has appeared in the Search Engine Journal and Martech Zone.