Mobile now accounts for the majority of mail. Analysis from Litmus shows 51 percent of mail messages were opened on a mobile device. Desktops account for just 31 percent while webmail is 18 percent.
While desktop mail use remains static, the last year has seen a 10 percent move from webmail to mobile.
The research also says 61 percent of webmail mail users open their messages on mobile devices.
Litmus says business users still prefer to use desktops to handle mail, while consumers mainly use smartphones.
Elsewhere in the analysis Litmus says Android phones have moved past iPads to become the third most important mail client behind iPhone and Outlook. The iPad is in fourth spot and Apple Mail is number five.
Litmus says it collected data from 320 million mail message openings worldwide to produce this report.