Open Rate is the total number of emails opened divided by the total number of emails delivered, usually multiplied by 100 to express the result as a percentage.

For example, if you send your e-mail to 1,400 recipients, 32 e-mails were more than once in the list, 5 are incorrect adresses, 10 have bounced back, and you get 594 read notifications, the open rate is:

Open Rate = Read / (Sent - Repeats - Incorrect - Bounced) x 100

Open Rate = 594 / (1400 - 32 - 5 - 10) x 100 = 43.9 %

So, you get read notifications for almost 44% of the total mails delivered, which is not bad at all.

MAILCast will do all this calculations (and many more) for you with all your mailings at once:

(Names blurred to protect our customer privacy)

Yo can see our current example in the first line. You could click on any of this columns in order to drill-down into the information, or export it to Excel, print it...

What's the real value of Open Rates?

And now the bad news: Open Rates are very inaccurate, so you can't trust them.

Wait a minute. So what? Might I ignore this metric?

Not exactly.

Every e-mail tracking system in the market obtains read notifications through a simple trick that is to include a unique hidden image (in fact a very small -1x1 pixels- one) in every mail sent, which "calls home" when it's displayed in e-mail clients.

The problem with this trick is that if your recipients read your e-mail when they are offline, or have the images blocked, or read it through a mobile device, and so on, these notifications never get to the stats server, and they are not tracked as reads, although they must be.

So, open rates are intrinsically inaccurate and you can't relay on them directly.

The point is that you must always use open rates comparing them with similar e-mailings you had done in the past. So if, for example, you send two similar e-mails to very similar groups of people (or the same group), and you perceive significative differences between the two open rates, then probably you have done something that has direct impact in the interest of your target (eg: the subject line).

This is the way to go with open rates: always use them as a comparison pattern, not as an absolute value.