Freelance writing


Content strategy

Improving Mailchimp open rate accuracy

November 15, 2018

This post teaches you how Mailchimp track email opens and, more importantly, how to avoid your email opens not being tracked.

Mailchimp shows you how many people on your mailing list open each email:

This is useful because you can track engagement and correlate it with subject lines, email content, and more, to get an idea of how effective your email campaigns are.

But how accurate is the Mailchimp open rate number?

In the “How Open Tracking Works” section of the relevant page in Mailchimp’s support pages, they give this info:

Each time you send an email campaign through Mailchimp, we embed a tiny invisible graphic in the bottom of your HTML email.

When someone opens your email with images turned on, that graphic is downloaded from our server, and it’s recorded as an open on your campaign report.

This is the industry standard. It is elegant and not intrusive. However it does have problems.

How to avoid opens not being tracked

Because the tracking graphic is at the bottom of your email, it will not be downloaded if your email is truncated in the reader’s inbox:

If you see this link in your newsletter, it will not be tracked as an open unless the reader clicks ‘view entire message’.

I recommend sending a test email through Mailchimp, and checking the full email is visible within your inbox.

Remember this is based on the size of the email rather than the word count. This means if you use more hyperlinks, or more HTML styling within your email, your code will be longer and the size will be bigger as a result.

Different email providers truncate emails at different lengths, but they float around 100kb:

  • Yahoo: 100kb
  • Gmail: 102kb
  • Outlook & Hotmail: not readily available

Because the tracking graphic is a graphic, this method doesn’t work with plain text email campaigns. Opt for HTML emails if you want to track engagement.


I’ve been informed about a Gmail extension called Hunter which lets you see when your emails are opened. Great for tracking engagement and planning follow-up action if you do your outreach through Gmail.