Free HTML email tester

A free HTML email tester is vital for email marketing campaigns so you can ensure the success of your HTML emails across mobile devices and email clients. Once you’ve run a test, Mailgun provides an easy way to send your emails for free.

Why email testing matters for email marketing campaigns

No one should ever send email marketing messages, such as email newsletters, without first testing the messages. This way, they will stay out of spam filters, they’ll look great on mobile devices, and they’ll achieve positive results. If you don’t test your email, you could be heading for failure, not success.

Three email icons lined up diagonally.

You can test subject lines

One of the biggest advantages of using an email testing tool is the ability to check email subject lines. Why is this important? Because 47 percent of recipients open an email based solely on the subject line. The open rate depends heavily on how many words are in a subject line. Subject lines with 6-10 words perform best, but subject lines with up to five words aren’t far behind. Various tools can test the spam score, readability, effectiveness, sentiment, keywords, and other facets of a subject line. Through testing, you can tweak subject lines until you find one that’ll boost open rates.

A graphic illustration of mobile email templates.

You can test email clients

Another key benefit of an email testing tool is the functionality that enables tests of popular email clients like Google, Yahoo, Apple Mail,, AOL, and Lotus Notes. This kind of testing is critical because different email clients behave differently. For instance, your email design might look awesome on Google but break on Yahoo. There is no single standard for how email marketing messages are rendered by email clients. To avoid rendering issues, email previews are available through tools from email marketing services such as Email on Acid, EmailReach, Inbox Inspector, Mailchimp, and Campaign Monitor. With these previews, you gain real-time perspective on how your emails would appear when sent via many different clients.

You can preserve email marketing resources

In 2020, the global email marketing market was valued at $7.5B. That’s a hefty investment, for sure. But the investment in email marketing pays off. It’s estimated that the median ROI for email marketing is an eye-opening 122%. Those numbers demonstrate how crucial it is for any email marketer to test HTML email templates so that money isn’t wasted and revenue continues to flow. A number of free tools can help you accomplish that, incorporating a fundamental step into your email marketing campaigns.

Results for an email verification check.

Sign up today

You can improve your email delivery

Once you’ve chosen the right email testing tools for your marketing initiatives, rely on Mailgun to make sure your email deliverability is strong. You can test our high-quality email services by signing up for a free trial today!

Check out our plans to bundle together features for better deliverability. For businesses that send over 100,000 emails.

Other features

Explore beyond HTML email

Mailgun has a variety of features for companies in need of free HTML email testing.

Window icon


Open email icon

Use Cases

See what you can accomplish with the world's best email delivery platform

It's easy to get started. And it's free.
CTA icon