Microsoft 365 Mailbox Storage Increase: 50GB to 100GB Rollout

Microsoft 365 mailbox storage increase is rolling out in 2026. Learn how the new 100 GB Exchange Online capacity impacts Business users and custom IT quotas.

Running out of primary email storage frustrates users and creates unnecessary helpdesk tickets. Microsoft is finally addressing this common headache by expanding the primary Exchange Online mailbox capacity for eligible Business Basic, Business Standard, and Business Premium users.

The server-side rollout began in June 2026 and continues through September. Microsoft is doubling the previous 50 GB entitlement to a 100 GB primary mailbox quota. IT administrators have received advance tenant notifications via the Message Center regarding this free capacity boost.

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