The new Outlook app offers new features for mobile users, including a way to sort and filter important emails.
It offers a "focused inbox" which learns "about you and gets even more tailored to your priorities," the blog said.
The move comes a day after US online giant Amazon announced plans to offer a cloud-based email and calendar service to directly compete with Microsoft Outlook and others.
The service dubbed Amazon WorkMail "enables users to send and receive email, manage contacts, share calendars and book resources using the same email applications they use today" including Outlook and services like Google Apps.