The new app is expected to be an addition to Outlook, which will facilitate faster and natural conversation without addition of frills like subject lines, salutations, and signatures.
The discovery was made by Twitter user h0x0d, who spotted a download page with text for the new app, marked ‘Microsoft Confidential’ and titled ‘Flow by Outlook’.
The text said: "Use Flow with anyone, it’s email: Reach anyone with an email address and all conversations for you and others are also in Outlook. Together, you can use Flow and Outlook interchangeably to participate in the same conversations.
"Focus on what’s important: Only conversations started in Flow and their replies show up in Flow, not your whole inbox. Focus on your most important person-to-person conversations without the noise."
Microsoft has made changes to its Outlook app for the latest Windows Phones, which is presently in preview for Windows 10 Mobile.
The Outlook app looks similar to its predecessors but it is based on different codes.