Did you realize how quickly mobile users have taken to accessing their email via mobile devices? It’s growing at a very rapid rate. Due to the rise of smartphone penetration, the number of users accessing email via their mobile devices grew by 36% from November 2009 to November 2010 according to a recent study by comScore Media Metrix and MobiLens. During this time, the number of visitors to web-based email sites declined by 6%, and the time spent on those sites decreased by 9%.

The rise in popularity of the iPhone has been a leading reason for the shift. A new Knotice study shows that 13.36% of emails are opened by a mobile operating system or device, with the iPhone leading the way at 8.74%. The iPad (at 2%) and Android (at 1.9%) are gaining ground quickly, with other Windows, Blackberry and Palm devices making up the remaining users.

With the rise in smartphone penetration, which is projected at 35% of all mobile users now and expected to reach 50% by the end of the year according to Nielsen, the mobile user base is only going to continue to grow.

With growth occurring across all mobile categories, its no wonder that the daily use of email showed an increase of 40% (to 43.5 million users) as mobile users turn to their smartphones on a regular basis to check their inbox.

In a relatively short period of time, the adoption of mobile email has reached 78% of the smartphone population. It shows how quickly shifts can occur in the digital landscape, and how brands need to prepare themselves to reach their subscribers across multiple platforms and devices.

In upcoming posts we’ll show how you can improve your campaigns for mobile users. Stay tuned!