The Likes feature will come first to Outlook on the web -- the version of Outlook formerly known as Outlook Web App. The feature will begin rolling out first to Outlook on the web starting September 30 to Office 365 First Release customers who have an Office 365 business plan that includes Exchange Online.
Microsoft plans to roll out the Like feature more broadly to Office 365 commercial customers with Business, Enterprise, Education and Government plans starting in late October. The Mention feature will start rolling out to First Release customers in mid-October and to the rest of eligible Office 365 commercial users starting in mid-November.
Microsoft also is planning to make these features part of Outlook.com, starting with Outlook.com users who have been moved to the new version of the service. Those users will start seeing Mentions in December. The Mention feature also will be added to Office 2016 clients for Windows and Mac, as well as Outlook for iOS and Android, in the first half of 2016.
More details on when the Like feature will come to other Outlook users will be available "at a later date," Microsoft officials said.
Microsoft seems to be intent on showing that email can be useful to those who think of it as an antiquated, static mode of communication. I'm not so sure I want or need likes or mentions in my work mail. Maybe there will be a way to turn this off, the way I can turn off Clutter and Conversation View in Outlook. So far, I haven't heard whether this will be an option.