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Why test the deliverability of your emails before sending them?

Since I have been doing training on deliverabilityThere is always a part that is rarely done by my marketing friends... Testing your e-mail before sending it to your subscribers. If some clearly don't have the time to do it, others would like to do it but don't know what to test... Hence this article!

Why test an e-mail?

Before we give you all the tips you need to test your emails, it's important to understand why you should do it!

Here are some good reasons:

  • Know at a given moment its reputation level on the main ISPs/Webmails present in its database (identify possible blocking or abusive spamming).
  • Ensure that your email is displayed correctly on the different devices (Mobile vs. Desktop) and the different applications (mobile vs. Webmail).
  • Improve your marketing practices (know the best time to target your subscribers, select the best content for your subscribers, ...).

The main objective is to make sure that no blocking element (a block, a spamming, a break in your e-mail or a too strong marketing pressure) degrades your reputation or deteriorates your performance.

Testing yes, but what do I test concretely?

The few reasons given above will already give you some idea of what to test, but in concrete terms you will have to test everything you can.

Here's a pretty comprehensive list of things to check:

The reputation of all areas

You will have to make sure that no domain (sender, reply, tracking, image hosting) present in your e-mail is listed on one or more blacklists, on one or more ISPs.

The reputation of IPs

You will have to make sure that no IP is listed on one or more blacklists, on one or more ISPs.

Authentication systems

You will need to make sure that your authentication systems are properly set up (I'm talking about SPF, DKIM and DMARC).

Validity of the sending, reply and technical addresses

You will have to make sure that all the addresses used exist (each address must exist and be recorded) and do not return bounces.

The spam score of your e-mail

You will have to test the score of your e-mail (via spam assassin or another tool) in order to know if your e-mail potentially presents a delivery risk.

The content of your e-mail

Here you need to test the content of your message. Is it relevant? Is it well placed in your e-mail to attract a maximum of clicks from your subscribers?

The subject of your e-mail

Here you have to be sure that your subject line is relevant and that it will make your subscribers open your e-mail. An A/B test can help you to test your objects.

The rendering of your e-mail

You will have to make sure that your e-mail is displayed everywhere, whether it is on a mobile or on a desktop.

The unsubscribe link

Here, you will have to test the most important link of your e-mail, namely your unsubscribe link and therefore make sure that it is present and functional.

The HTML code of your e-mail

Here you will have to make sure that your code is compliant with the different email standards so that it will be displayed correctly or that the Anti-Spam filters will not tag it as spam.

Marketing pressure

Here you need to make sure that you are not over-soliciting your subscribers with your communications. You can use your router's tool (if it has developed one) to manage your commercial pressure.

The best time to contact your subscribers

Here you will need to analyze your subscribers' behavior in order to choose the right time to communicate with them. Use the dashboards provided by your router to help you find the best time to contact your subscribers.)

Which tool(s) should I use to test everything?

Now that you have a checklist at your disposal, you need to know how to check all these elements. Some of them can be done with the tools provided by your professional router, others can be found on specialized sites.

Here is an overview of some of the tools you can use:

  • Mail-tester - (free): Your e-mail will be submitted to a battery of tests (spam score, authentication system verification, ...).
  • MxToolBox - (free): With this tool you can check all your technical configuration: blacklists, IP configuration, authentication systems, ...
  • W3C - (free): Useful tool to validate the HTML code of your e-mail.
  • 250Ok - (paying) : Complete tool for deliverability monitoring used by Badsender, you have at your disposal different modules: a module to monitor your reputation (blacklists, Microsoft, Signal-Spam, authentication systems), a module to perform seedlist tests (ISP/Webmails, message content test, ...), a module to monitor DMARC (and see who is trying to impersonate you), a module to test the display of your e-mail (via Email On Acid), a module to analyze your audience (better know the behavior of subscribers).

Do not hesitate to contact us for more information!


In conclusion, the purpose of this article is not to make you spend a whole day testing all your e-mails but to give you all the tips that will allow you to improve the performance of your campaigns. It would be a shame to forget, for example, to do a seedlist test beforehand on a strategic campaign and to find out after sending the campaign that the IP was blocked at Orange... that would be bad luck 😉

Need support in these areas? Discover the services offered by our emailing and eCRM agency.

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