Create a Free SMTP Server (Plus Tips about Shopping for vs. DIY-ing)


SMTP servers are a great way to send email, but figuring out the best solution for your business can be difficult. 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 covered how to get started with SMTP servers, what to consider when buying or building an SMTP server, and how to set up an SMTP server for free with Twilio SendGrid.

The basics of creating an SMTP server

A SMTP or Simple Mail Transfer Protocol server, is an application that helps senders to receive and send outbound email communications. When you send your messages, SMTP servers determine which servers your messages are forwarded to. Then inbox providers on the receiving end download the content of your email and deliver it to the inbox.

When setting up an SMTP server, you have the choice of building a local 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 usually only created for testing purposes as they are not easily scalable and often result in poor delivery rates. Other solutions for local 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 whether to build all of the decorations for your wedding yourself or do the home renovations yourself, building your SMTP server yourself has significant advantages and disadvantages. Cost, scalability, and support are all factors you need to consider to determine whether it is worth the time and effort building your own SMTP server.

To help you decide whether or not to build your own SMTP mail server, we’ve compiled a list of the pros and cons of having a local SMTP server (and we’ll go into more details below).

Advantages and disadvantages of a local SMTP server


      • You are in complete control of your own system and facility.
      • You can manually monitor and optimize your shipping practices to improve your deliverability.
      • You can set up your own authentication protocols.


      • There wouldn’t be a real support system, which means outages could be tedious and harmful to your business.
      • The deliverability of e-mails is constantly changing and requires consistent maintenance.
      • You will not have expert support if the authentication setup process fails.

Cost & time

There may be higher upfront costs if you decide to buy a cloud-based solution for your SMTP server. However, you cannot set up and forget about an SMTP server. The construction costs not only time and money, but also maintenance. This requires someone to manage the server full-time, update hardware and software as needed, and fix any errors that occur.

An SMTP server is not something you can set up and forget.

An email service provider like Twilio SendGrid offers 99.9% availability, but it took years of fine-tuning to achieve this. Setting up your on-premises solution is likely to experience downtime as you optimize and scale your program. The cost of an email outage to a business can be astronomical. So take this into account when considering whether to build or buy.


If you only want to send a few hundred emails at a time and don’t want to scale your SMTP server to thousands or tens of thousands of emails, then a local SMTP server might be the perfect solution for you.

However, if you want to expand your e-mail program to communicate with hundreds of thousands of customers (maybe even millions!) On a regular basis, it becomes incredibly difficult to scale an on-premises solution to this magnitude. Twilio SendGrid has spent years perfecting its SMTP server so that it can easily scale and send as many as 5.8 billion emails in a day.

Twilio SendGrid can send up to 5.8 billion emails in a day.

In addition to the actual number of e-mails sent, as e-mail programs grow, most people want to know how their e-mails work. A solution like Twilio SendGrid provides insight into these details, such as: B. Delivery Metrics.


If something goes wrong with your email program on the Twilio SendGrid platform, you’ll always have someone to count on, whether it’s ours Support team or Deliverability Experts. From changing requirements for inbox providers to complying with legal requirements or monitoring your rejection entries, there is always something new to monitor. This is why it is so helpful to have a team of experts that you can fall back on at any time.

However, if something goes wrong with your local program, you will have to rely on your in-house developers and email experts to fix the problem.

An on-premises SMTP server might be the right solution for smaller businesses that don’t want to scale, but they still need someone to manage and maintain the server. For most businesses, we’ve found that cloud-based SMTP solutions are better suited. Cloud-based solutions are more reliable, cost-effective and save the company time so that you can focus on what really matters – growing your business.

Further information on the purchase vs. DIY decision can be found in our guide: Your Guide to Email Infrastructure: Build or Buy It?

How to create an SMTP server with Twilio SendGrid

Now that you understand the pros and cons involved in creating or buying an SMTP service, let’s see how you would set one up with Twilio SendGrid.

  1. Send a test email using Telnet
      1. Before you can set up your SMTP server with SendGrid, it is helpful to first send a test email with Telnet. This will help senders familiarize themselves with using the SendGrid X-SMTPAPI header.
      2. For the test email you need to:
        1. Set up SendGrid account
        2. Create an API key
        3. confirm your identity
      3. With these materials in place, you can open your terminal and follow these step-by-step instructions How to send a test email using Telnet.

2. Integrate your servers with the SendGrid SMTP service

      1. To integrate the SendGrid API, you need to create an API key with at least mail permissions.
      2. Set the SMTP server to:
      3. Enter your username and password according to the API key you created in step 2a.
      4. Select the port. Your options are port 25, 2525, or 587 for TLS ports. Or port 465 for SSL.
        1. Port 25 is often not accepted by all servers. We recommend using port 587 for most broadcasts. For a refresher on ports, see our article, What is the difference between ports 465 and 587?

3. Compose your email with X-SMTPAPI headers

      1. Now that you’ve got the basic setup down, it’s time to add the fun things to your email (subject line, recipients, scheduling, woohoo!). X-SMTPAPI is an easy way to customize the emails you send with different filters. For example, you can use replacement 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 trouble creating an SMTP email account, don’t worry, we have resources and email experts to help you with that.

      • SMTP errors and troubleshooting: Receiving an error but not sure what it means? Here is a Failure code to help you troubleshoot.
      • Support: Stuck and don’t know how to move on? Get help from our Support team.
      • Expert services: Do you need help implementing your email program right from the start? Look no further – our email experts have you covered Implementation services to get you set up right the first time.

Create your free SMTP server and start sending

Are you ready to build your free SMTP server and start sending? Integrate into the Twilio SendGrid MTA in just a few minutes and reliably send emails to your customers without having to worry about server administration. 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 get you started:

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