Microsoft to announce apps and add-ins for Outlook.com, detail plans for opening up Office as a platform at Build 2015 this week
Tom Warren / The Verge :
Context & Ripple Effects
Build 2015 is where Microsoft stops treating Office as a sealed suite and starts treating it as an extension surface, starting with apps and add-ins for Outlook.com, which is being rebuilt on Office 365 under the hood. The related coverage shows this was not a one-off gesture but the opening move of a pattern.
The arc since then runs through add-ins reaching Outlook on iOS with partners like Giphy, Evernote and Trello, Microsoft [[a:878271|offering rivals access to Outlook add-ins as part of winning EU clearance for the LinkedIn deal]] — proof the openness had acquired regulatory value — and eventually plans to integrate OpenAI's language tech directly into Word and Outlook. The same open-the-platform playbook resurfaced at Build again when Microsoft moved to open Xbox to developers.
First-order effects
- Third-party developers get a supported distribution channel inside Outlook.com and Office, while consumers see external services embedded in their inbox rather than bolted on beside it.
Second-order effects
- The add-in surface becomes strategic leverage beyond product features — Microsoft later trades rival access to Outlook add-ins for antitrust approval of the LinkedIn acquisition, turning platform openness into deal currency.
Third-order effects
- If the pattern holds, Office's evolution from closed suite to extensible platform is what makes later layers possible — the same Word and Outlook surfaces Microsoft planned to thread OpenAI's models through are only integrable because they were first opened to add-ins.
The trend: Microsoft has spent a decade converting its flagship products from closed applications into extensible platforms — first Office, then Xbox — making the app surface itself the integration point for partners, rivals and eventually AI.