Mobile Email Adoption
Why is mobile email adoption important? First you have to understand a little about how email open rates are calculated. When an email marketing system sends an email, it includes an invisible image in the email called a tracking pixel. When the email client asks to download the tracking pixel, the email marketing system knows the email was opened.
Desktop clients like Outlook and several webmail clients block images from loading by default. They do this to protect the user's privacy, but the result is that the system sending the email has no way of knowing that email was opened unless the subscriber explicitly downloads images. Mobile email clients generally don't have the same limitation, requesting the images immediately after the email is loaded. So as mobile adoption increases, so will open rates, simply because more opens get counted from mobile devices than are counted from webmail or desktop clients.
The Gmail Factor
Initially, many in the industry were concerned this would reduce open rates, because the tracking pixels would be opened once by google and then shared to all the subscribers of that email using Gmail. In reality, since each tracking pixel had a separate web address (URL), each open was properly accounted for. Only repeat loads of the same tracking pixel by the same email subscriber were affected. Since images are now loaded by default, open rates on Gmail actually went up significantly, with Litmus reporting an open rate increase of 243%.