How to Setup a Free SMTP Server (Buying vs. DIYing)

August 02, 2023
Written by
SendGrid Team
Opinions expressed by Twilio contributors are their own

How to Setup a Free SMTP Server (Buying vs. DIYing)

Want to know how to setup SMTP servers to send emails for your business? You've come to the right place.

SMTP servers are a great method of sending email, but it can be challenging to know the best solution for your business. Is it better to build an on-premise solution? Or, does it make more sense to use a hosted SMTP relay service provider?

In this article, we break down how to get started with SMTP servers, what you need to consider when buying or DIYing an SMTP server, and how to set up an SMTP server for free with Twilio SendGrid. 

How to setup an SMTP server

A Simple Mail Transfer Protocol or SMTP server is an application that helps senders receive and send outgoing email communication. When you send your messages, SMTP servers determine which servers will receive your relay messages. Then, inbox providers on the recipients’ end download the content of your email and deliver it to the inbox. 

When you set up an SMTP server, you have the choice of building an on-premise solution or using a hosted SMTP relay server service provider. 

While you could set up a simple SMTP server in Windows 10, macOS, or Linux, these servers are typically only for testing purposes because the servers aren’t easily scalable and often lead to poor delivery rates. Other solutions for on-premise mail servers include building on top of services like Postfix.

But, is it worth the time and effort? 

Should you create your own SMTP server?

Much like deciding to DIY all of the decorations for your wedding or DIY the renovations on your house, DIY-ing your SMTP server has significant advantages and disadvantages. Cost, scalability, and support are all factors you’ll have to consider to determine whether it’s worthwhile to put the time and effort into building an SMTP server.

To help you decide whether or not to create an SMTP mail server, we’ve compiled a list of the pros and cons of an on-premise SMTP server (and we dig into more details below). 

Pros and cons of an on-premise SMTP server

      • You have complete control over your system and setup.
      • You can manually monitor and tweak your sending practices to improve your deliverability.
      • You can set up your authentication protocols.
      • You wouldn’t have access to a true support system, meaning outages could be long and harmful to your business.
      • You have to consistently maintain the server as email deliverability is ever-changing. 
      • You won’t have expert support if the authentication setup process goes wrong.

Cost & time

There may be a higher upfront cost if you decide to buy a cloud-based solution for your SMTP server. However, an SMTP server is not something you can set and forget. It not only takes time and money to build, but it also takes time to maintain. This requires someone to manage the server full time, update hardware and software as needed, and troubleshoot errors. 
An SMTP server is not something you can set and forget.
An email service provider (ESP) like Twilio SendGrid offers a 99.99% uptime, but this took years of fine-tuning to achieve. As you set up your on-premise solution, you’ll likely have outages as you tweak and scale your program. The cost of an email outage to a business can be astronomical, so factor that into your build vs. buy considerations.


If you only plan on sending a few hundred emails at a time and have no desire to scale your SMTP server to accommodate thousands or tens of thousands of email sends, then an on-premise SMTP server could be the perfect solution for you. 

But, if you want to grow your email program so that you regularly communicate with hundreds of thousands of customers (maybe even millions!), it will be incredibly challenging to scale an on-premise solution to that magnitude. Twilio SendGrid has spent years perfecting its SMTP server to be able to easily scale and send as many as 5.8 billion emails in one day.
Twilio SendGrid can send as many as 5.8 billion emails in one day.
In addition to the actual number of emails sent, as email programs grow, most people want to understand how the emails sent perform. A solution like Twilio SendGrid provides insight into those details, like delivery metrics.


If something goes wrong with your email program on Twilio SendGrid’s platform, you always have someone you can lean on, whether it’s our Support Team or Deliverability experts. From changes to inbox provider requirements to regulatory compliance or monitoring your deny listings, there will always be something new to monitor, which is why it’s so helpful to have a team of experts you can leverage at any time. 

However, when something goes wrong with your on-premise program, you’ll have to rely on your in-house developers and email experts to mitigate the problem. 

An on-premise SMTP server may be the right fit for smaller businesses that aren’t looking to scale, but it will still require someone to manage and maintain the server. For most businesses, we’ve found cloud-based SMTP solutions to be a better fit. Cloud-based solutions are more reliable, cost-efficient, and save time, so you can focus on what matters most—growing your business. 

For more information on the buy vs. DIY decision, take a look at our guide: Your Guide to Email Infrastructure: Build It or Buy It?

How to Setup SMTP server with Twilio SendGrid

Now that you understand the pros and cons that come with building or buying an SMTP service, let’s take a look at how you would set one up with Twilio SendGrid.

1. Send a test email with Telnet
      1. Before you can set up your SMTP server with Twilio SendGrid, it’s helpful to first send a test email with Telnet. This helps senders become more familiar with how to use Twilio SendGrid’s X-SMTPAPI header. 
      2. For the test email, you'll need to:
        1. Set up a Twilio SendGrid account
        2. Create an API key
        3. Verify your identity
      3. With those materials in place, you can open your terminal and follow this step-by-step tutorial on how to send a test email with Telnet
2. Integrate your servers with Twilio SendGrid’s SMTP service
      1. To integrate with Twilio SendGrid’s API, you’ll need to create an API key with at least mail permissions.
      2. Set the SMTP server to
      3. Fill in your username and password according to the API key you created in step 2(1). 
      4. Select the port. Your options are port 25, 2525, or 587 for TLS ports. Or, port 465 for SSL.
        1. Not all servers accept port 25. We recommend using port 587 for most sends. For a refresher on ports, check out our article, What’s the Difference Between Ports 465 and 587?
3. Build your email with X-SMTPAPI headers
      1. Now that you have the basic setup taken care of, it’s time to build out your email with the fun stuff (subject line, recipients, scheduling—woohoo!). X-SMTPAPI is an easy way to customize the emails you send using different filters. For example, you can use substitution tags to personalize the content of each recipient’s email.
      2. To learn more about what you can do with X-SMTPAPI headers, check out our docs article.
If you run into any issues creating an SMTP email account, not to worry, we have resources and email experts to help you along the way.
      • SMTP errors and troubleshooting: Getting an error, but you're not sure what it means? Here’s an error key to help you troubleshoot.
      • Support: Stuck and can’t figure out how to move forward? Get help from our Support Team
      • Expert services: Want help from the get-go to implement your email program? Look no further—our email experts provide implementation services to set you up right the first time.

Create your free SMTP server and start sending

Ready to set up your free SMTP server and start sending? Integrate in minutes with Twilio SendGrid’s MTA and reliably send emails to your customers without having to worry about server management. Sign up for Twilio SendGrid’s free SMTP service.

Twilio SendGrid’s resources are here to help. When you’re ready to send, here are some resources to help get you started:

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