If you always respond very quickly to messages from a certain person, that sender is likely to be important to you — and is probably your boss. If you leave messages from another sender for three weeks and then delete them almost as soon as you open them, that person is probably not very interesting to you. The Clutter service in Office 365 uses that to filter those less-interesting messages into a folder (which automatically shows up as a favorite folder in Outlook so it's easy to spot when messages have been filed there). If the Office Graph figures out who your boss and your direct reports are, Clutter never filters out mail from them.
You can train Clutter by marking messages as clutter or not clutter — or just deleting and ignoring messages you don't care about and dragging messages you do care about back to the inbox. Clutter can cope when you reply to the wrong message or ignore something that's important (perhaps because you make a phone call instead — which Clutter might one day know about if you use Lync).
The danger with automated systems is that if they get things wrong, you stop being able to rely on the systems they're trying to enhance. False positives mean spam filters still block legitimate messages sometimes — but recommendation algorithms are good enough that we rely on them for Web search and shopping on Amazon and picking movies on Netflix.
Perhaps because it's not too ambitious and tends to err on the side of caution, Clutter is proving popular, especially with users who don't already have strong email management systems. And unlike clients like Google's Inbox or Microsoft's new mobile Outlook tools, which also try to highlight interesting messages, it doesn't mean asking users to change their mail tools — or asking companies to feel comfortable with email and credentials being in cloud systems they don't control. Users have to use Outlook Web Access to opt in to the system (and it's not available for any users you're keeping in on-premises mailboxes), but they can still see Clutter messages in iOS Mail or whatever mail client they prefer.
Microsoft says it's working to unify Clutter and the mobile Outlook Focused view, so this looks like a useful tool that will continue to be developed.
Niche or Next-Generation?
Getting people to put documents in repositories rather than keeping them on their own PCs solves the retention and security problem but replaces it with a discovery problem. The Office 365 First Release program includes a more ambitious and more experimental system, Delve, which also builds on the Office Graph to find documents users would otherwise have to dig for. It's a portal on the Office 365 site that shows you either the documents you've shared with people and when they've made changes to them, or the documents other people have shared with you.
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