Glossary
Focused Inbox
By Emil Björk · Microsoft ecosystem consultant, Gothenburg
An Outlook feature that automatically separates important mail from low-priority mail using mailbox-side machine learning.
Focused Inbox is the Outlook feature that automatically splits the inbox into two tabs — Focused (likely important) and Other (likely low-priority) — using mailbox-side machine learning trained on the user's behaviour, sender reputation, and content signals. The model is per-mailbox and adapts over time as users move messages between tabs. Available in Outlook for Windows (classic and new), Mac, web, and mobile. Successor to the older Clutter folder, which moved likely-unimportant mail to a separate folder rather than splitting the inbox. Different from Junk Email (spam filter, EOP-driven); Focused Inbox sorts mail that has already passed spam filtering.
Worked example
A regular internal newsletter from IT keeps landing in a user's "Other" tab, so they consistently miss the monthly security reminder buried in it. The user right-clicks one instance and selects "Move to Focused" — a single action that both moves that message and retrains the mailbox's own model to treat future mail from that sender as important going forward. A few weeks later, without any further action, the newsletter reliably appears in Focused, because the per-mailbox model adapted to that one explicit correction rather than needing an admin-level rule.
Common pitfalls
Assuming Focused Inbox is a spam filter, and reporting a Focused/Other misclassification as a security issue, is a very common help-desk confusion — Focused Inbox only sorts mail that has already passed Exchange Online Protection and Defender for Office 365 filtering; it has nothing to do with whether a message is dangerous. Expecting a single "move to Focused" correction to instantly and permanently fix classification for an entire team is a related misunderstanding — the model is per-mailbox, so one user training theirs to treat a sender as important does nothing for a colleague's separate mailbox. And overlooking that Focused Inbox can be turned off entirely, per user, in favour of a single traditional inbox is worth knowing when supporting users who find the two-tab split more confusing than helpful — it's a preference, not a mandatory feature.