Microsoft announced an update to its Outlook apps for iOS and Android, as it revealed that the apps have 30 million active users generating 1.2 billion sessions per month.

“These numbers show what we’ve known for some time, despite reports to the contrary, that email is a key communications channel across all parts of our life, and there is growing demand for a mobile email experience that helps to effectively manage those conversations,” Javier Soltero, corporate VP for Outlook, said.

Having acquired calendar app maker Sunrise earlier this year, Microsoft said the Sunrise team is now part of the Outlook product team and that Outlook will eventually replace the standalone Sunrise app.

“We will leave Sunrise in market until its features are fully integrated into Outlook, the exact timing of which we will communicate in advance,” it said.

Microsoft’s updated Outlook for iOS will have a “clean, refined new look” making it the “best designed, most powerful mobile email app available”, the company said. Roll out of this has begun.

The updated Android app will be available from early November, and will include a “redesigned header, message list and compose experiences” in hopes of making Outlook “feel like a natural part of Android”.