Microsoft doubles Business mailbox size to 100 GB
Reviewed by Helen Jones
Microsoft is raising primary Exchange Online mailbox quotas on Microsoft 365 Business Basic, Standard, and Premium from 50 GB to 100 GB. The change is delivered through an extra service plan and began rolling out in mid-June 2026, with Microsoft aiming to finish by the end of September 2026. Archive mailboxes are unchanged: Basic and Standard still get 50 GB of archive space, while Premium keeps auto-expanding archive up to the usual high limit. Shared and resource mailboxes follow separate rules, and not every user mailbox in a tenant receives the new quota on the same day. Related packaging and pricing updates took effect from 1 July 2026. The larger primary quota reduces one common reason firms bought Exchange Online Plan 2 only for more inbox space.
Before this change, many mid-size Business tenants hit the 50 GB wall after years of attachments, shared-mailbox copies, and never-deleted threads. People either lived with constant cleanup pressure, paid for a higher Exchange plan they did not otherwise need, or leaned on archive and third-party tools mainly to free primary space. After the upgrade, primary capacity doubles for eligible user mailboxes, so the full-mailbox warning should appear less often. That does not make email easier to work. A 100 GB inbox is still a pile of unread items, flags, and old projects with no trusted triage rhythm. Archive remains a separate bucket for Basic and Standard, so retention, legal hold, and long-term findability are still different problems from raw free space.
Analysis
Treat this as a quiet capacity change to verify, not a reason to stop cleaning mail. In Outlook, open mailbox settings or account information and confirm whether your quota already shows 100 GB; if you still sit at 50 GB, wait for the service plan rather than opening a ticket on day one. Keep one simple rule for mail older than your real working window so the extra space does not become a larger place to lose follow-ups.
Source note
Pulse published by Collab365 Spaces, reviewed by Helen Jones on . Cite as "Microsoft doubles Business mailbox size to 100 GB", Collab365 Spaces. 3 sources referenced.