Opens or open rates measure how many people opened up an email and looked at it. In most cases, they aren’t read, but there’s no guarantee they did any more than glance at it, and there is no way to track how long they looked at the email. Though it is a general indicator of subject line effectiveness, it can be a misleading metric for online marketers.
The "open rate" for an email campaign is a measure of how many recipients viewed an email. It's important to understand that open rates are not a 100% accurate measure.
Opens can be tracked in HTML emails because they include a tracking pixel, which is a tiny, invisible image that is displayed when the subscriber opens your email. When that image is downloaded from the web servers, the email is recorded as being opened in most cases.
There are various reasons why the number of opens can be over-reported, and they can also be under-reported. Recording an open can only happen if the reader's email client can display HTML with images, and that option is turned on.
Similarly, people may choose to read your HTML email without displaying images not tobe recorded as an open either.
Even though email open rates are not a 100% accurate measure, it is incorrect to assume that this metric has no value. Paying attention to email open rate trends is very important because it leads to questions like “are my open rates trending up or down?” and “Are some customer segmented lists performing better than others over time?”
Therefore it can be said that open rates are not wholly accurate, but to dismiss them completely would be an error. It is best to keep watch for open rate trends and consider improving the trend with segmented email lists, targeted email segmentation, and timely, relevant communications.
To calculate the email open rate of a digital campaign, the following formula should be used:
Email Open Rate = Number of Emails Read / Number of Delivered Emails ×100
For example, if you send out 12 emails and 2 of them bounce, the number of delivered emails becomes 10. If out of those emails, five are opened, your open rate is then 5/10 = 0.5. Multiplying that by 100 gives you an email open rate of 50%.
When looking at the reports of a campaign that has just been set, it is possible to notice that there are two types of opens; opens and unique opens. There is a slight difference between these.
An open is the number of times the email has been opened.
A unique open is how many people have opened your email.
So the difference is you could have 200 opens on an email, but only ten people have opened it ten times. Or you could have 200 opens and 200 people had opened it.
Contact A opens the email five times.
Contact B opens the email three times
Contact C opens the email ten times.
When you look at the reports, it would say 18 opens, but there would only be three unique opens.