Five Ways to Test an Email

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I recently wrote about the importance of testing your email campaigns. There are dozens of popular email clients today and each one has the potential to display your email campaigns differently. Testing is a vital step in the email marketing process and helps ensure that your message gets across in its intended manner.

But, what are some of the different ways we can actually test an email design? Depending on what part of the email process you are responsible for, there are a number of solutions for testing out an email before it is sent—each with its own advantages and disadvantages. Let’s take a look at a few of them.

Sending Through an ESP

Most email marketers are familiar with email service providers (ESPs) like MailChimp, Campaign Monitor, ExactTarget, and Silverpop. Even if you’re not logged in everyday, chances are that you’ve spent at least a little time in your ESP. Apart from organizing subscribers and tracking metrics, ESPs are one of the best ways to test an email campaign before it is sent to a list.

Most ESPs make testing an email an easy part of the campaign setup process. Once you upload your HTML to the ESP or edit a pre-existing template, you will likely see an option to send a test campaign to an email address.


This is an excellent solution for sending test emails for two main reasons. First, it is integrated into a process that you already use. Second, it gives you the most accurate rendering of your email. ESPs have been known to alter existing code, inline CSS (even if you don’t want them to) or inject their own code into emails when uploading or sending campaigns. Unfortunately, this can sometimes affect how the email renders in the inbox.

By sending a test email through your ESP, you can feel safe knowing that what you receive is exactly what your subscribers will receive.

An added benefit of using your ESP for testing emails is that most ESPs can be configured to pull in subscriber information when testing out things like dynamic content or personalization. Instead of seeing non-populated dynamic content and personalization strings, sending through your ESP allows you to see a campaign as if you were an actual subscriber.

Before emails are personalized.
Before an email is personalized.
After an email is personalized.
After an email is personalized.

While sending through your ESP may seem like the ideal solution for testing, it does have a few drawbacks.

Some ESPs require you to set up a testing list before you can actually send a test email, which can be time-consuming. Other ESPs force you to manually enter the email address or addresses you would like to send to (the number of which is sometimes limited). And, not everyone who needs to see a test has access to the ESP account. All of these things can slow down or even stop you from being able to use your email service provider for testing an email.


  • Part of an established process
  • Gives an accurate representation of the email code
  • Allows you to inject dynamic or personalized content


  • Can be time-consuming to set up test lists
  • Number of test addresses could be limited
  • Not everyone has access to an account
  • Only sends to specified addresses, limiting the number of clients you can test in
  • Can be expensive, depending on the ESP

Sending Through a Testing Service

For when you need to test out a design a bit quicker, you can use tools that act as light-weight email service providers. PutsMail, which was recently acquired by Litmus, is one such tool. PutsMail allows you to upload and send your HTML without the hassle of logging into an ESP or setting up test lists. You can specify exactly where you want the email sent and see it in your inbox in seconds.


Light-weight tools like PutsMail work beautifully during the actual design phase of email marketing. They allow designers and developers to quickly test iterations of emails without having to muddle around in a full-fledged ESP.

However, testing in this manner shouldn’t be utilized for final testing right before a campaign is sent. Since you are bypassing your ESP, you won’t be able to identify any issues related to injected or manipulated code. Likewise, you won’t be able to test out dynamic or personalized content.


  • Quick and easy
  • Doesn’t require ESP access or test lists
  • Free


  • Doesn’t give a true representation of how a final send will look
  • Can’t use dynamic or personalized content

Using a Build Process

Some email designers want a testing solution that is even more integrated into their workflow. These developers typically have an entire process set up to help with the creation of emails—usually using what’s known as a task runner, like Grunt.

Tools like Grunt allow designers to separate out components of their email, use CSS pre-processors like Sass or LESS, and run a command that essentially builds the final email for them. Brian Graves, a proponent of this type of workflow, recently wrote an excellent article on his process that’s worth checking out.

For advanced workflow junkies, there are a number of free tools that let you send test emails both to yourself and Litmus as part of the build process. Grunt-mailgun allows you to use the Mailgun service to send emails, which can be configured to send test emails to an account of your choosing.

The grunt-litmus plugin allows you to use your existing Litmus account for testing. When building your email with Grunt, it will kick off a new test in your Litmus account for review.


  • Allows great control over sending test emails
  • Can integrate testing into an advanced, efficient workflow for building email


  • Requires an upfront time investment to set up
  • Requires existing accounts for sending and receiving test emails
  • Geared towards developers

If you don’t want to invest the time into learning and setting up a complicated build process, you should check out Litmus Builder. Builder is a new tool for developing emails directly within Litmus. It allows you to code and preview a design right in the browser and, more importantly, start a complete Email Preview test from right within the tool.

Using Real Devices

Some email designers aren’t satisfied with previewing in their own accounts or using a service like Litmus. They prefer to see how a design looks and feels on an actual device. Most of us will preview an email on our own phones, tablets, and laptops, but a few intrepid email designers build what is known as a device lab.

Device labs are collections of various computers, phones, and tablets used to see how designs display on real, physical devices.

Email agency STYLECampaign is famous for their device lab, which consists of a plethora of devices for previewing client campaigns. Using the device lab, designer Anna Yeaman can identify display issues on the device causing them.

STYLECampaign's device lab.
STYLECampaign’s device lab.

While device labs can be amazing tools, they can be very expensive to assemble. Setting them up with the required email clients, accounts, and access to power can be time-consuming as well.


  • Allows you to see exactly how different devices render emails
  • Allows you to interact with a campaign, giving you a feel for how subscribers will actually use an email


  • Devices and data plans are expensive
  • Time-consuming to set up
  • Can get expensive to power dozens of devices
  • Requires a lot of space to house the lab

Email Previews with Litmus

Fortunately, you don’t need a full device lab to test your emails in over thirty different email clients. Litmus makes that easy. You can quickly preview your campaigns as well as run spam checks, link checks, and even color blindness tests to ensure that every subscriber is seeing your message as you intended.

More importantly, Litmus can (and should) be used in conjunction with the methods outlined above. We highly recommend sending emails via your ESP to Litmus. The same way that sending to yourself through your ESP gives you the most accurate representation of an email, it allows us to test and render the same code that subscribers receive.

If you don’t have access an ESP, you can always use PutsMail to send to your Litmus account or just upload the HTML itself.


No matter which method you choose to send emails for testing, you should make sure that they make their way into our Email Previews tool before sending to your subscribers.

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