Email campaign open rate statistic is not a good measure of success
Email open rate statistic is widely used as a credible measurable quantifier of success of email marketing campaigns. However, its significance nowadays should be disputed as it represents only a partial outlook on the recipient engagement with an email.
Firstly, email open rate is usually calculated by the amount of requests for a 1x1px transparent GIF image. This means that if a recipient is reading a text version of your email (say, on a Blackberry) or previews the content of the email in an a preview pane of an email client that blocks remote images by default, an open isn’t going to register. There are ways of tracking open rates of text email, but I wouldn’t recommend them.

