The open rate is the number of recipients who have been detected as opening the message at least once and may be expressed as a percentage of those who received it.
The open rate is a barometer of the efficacy of your email envelope-- the name it comes from and the subject line.
Your email marketing software should be able to detect opens if you are sending HTML email messages, generally by inserting a tiny image in the message. When the image is displayed, the software registers an open for that recipient.
The accuracy of tracking opens is limited by the tracking technology, which makes it prone to false positives and false negatives.
Beware of false positives: An open may be a false positive when an email client opened the HTML images in the preview pane. The recipient may never have actually read the message, but it is registered as an open anyway-- a false positive.
On the other hand, a recipient may in fact have opened and read your message without detection. These false negatives result when the reader has images suppressed or downloads and reads a message offline.
Given these uncertainties, the open rate can’t tell you the absolute number of people who read a particular message. Rather, it is useful for detecting trends.
The first step: determine what your baseline open rate is, and then see if a particular campaign is beyond the norm.
If your open rate averages 20 percent and a particular message jumps up to 25 percent, you can reasonably extrapolate that the "From" and subject lines were more effective. However, if your email open rate plummets to 10 percent, your message envelope may have been less effective, or recipients never had a chance to open it due to spam filtering.
A daily newsletter to a large opt-in list can expect opens in the 14 percent range. The open rate to a similar list could climb to 25 percent if the mailing frequency is less-- say, once a week.
Opens can be even higher if the recipients feel personally invested in the messages. A respected charity might see opens in the 30 percent range. And when the emails are paid subscriptions, open rates can skyrocket to 70 percent. Notice that even when recipients pay money to get the email messages the open rate doesn’t hit 100 percent.
Next: Clickthroughs