Microsoft has increased primary mailbox storage quotas from 50 GB to 100 GB for users on its Microsoft 365 Business Basic, Business Standard, and Business Premium plans. The change is part of a wider overhaul of Microsoft’s service packaging for 2026 and began rolling out in June, with the update expected to finish by September. Administrators were notified in advance via the Message Center. ([cybersecuritynews.com](https://cybersecuritynews.com/microsoft-expands-mailbox-storage-50gb-to-100gb/))
This storage boost applies strictly to the primary mailbox—it does not include archive mailboxes, nor does it bring in the additional compliance or feature rights tied to higher-tier plans like Exchange Online Plan 2. Existing limits on archiving or compliance remain governed by the user’s current plan. ([cybersecuritynews.com](https://cybersecuritynews.com/microsoft-expands-mailbox-storage-50gb-to-100gb/))
How It Works
The expanded quota is enabled by pairing two specific service plans. A user already on the BPOS_S_STANDARD plan (which carries a 50 GB limit) can add the EXCHANGE_STORAGE_50GB plan to reach the new 100 GB limit. Only when both plans are enabled does the full storage take effect. ([cybersecuritynews.com](https://cybersecuritynews.com/microsoft-expands-mailbox-storage-50gb-to-100gb/))
Admins can see and manage these settings in the Microsoft admin center under Users > Active users > Licenses and apps. Alternatively, admins can use Microsoft Graph PowerShell to check that the EXCHANGE_STORAGE_50GB service plan is provisioned, using commands that return the service plan names and their statuses. ([cybersecuritynews.com](https://cybersecuritynews.com/microsoft-expands-mailbox-storage-50gb-to-100gb/))
What Stays the Same & Caveats
Users with standalone Exchange Online Plan 1 licenses will still be subject to the 50 GB limit—those plans are not upgraded as part of this change. The new storage benefit does not stack beyond the highest applicable entitlement; for example, if a user has Business Premium and Exchange Online Plan 2, the limit is still 100 GB, not 150 GB. ([cybersecuritynews.com](https://cybersecuritynews.com/microsoft-expands-mailbox-storage-50gb-to-100gb/))
Also, if an administrator manually lowered a user’s mailbox quota (say from 50 GB down to 20 GB), that custom limit stays in place even after the service plan is provisioned. If the EXCHANGE_STORAGE_50GB plan is removed later, it does not reset or override any custom quotas that were in place. ([cybersecuritynews.com](https://cybersecuritynews.com/microsoft-expands-mailbox-storage-50gb-to-100gb/))
Because this rollout depends on licensing and service plan provisioning, not all eligible users will see the 100 GB quota at exactly the same time. Microsoft expects the change to be automatically applied for properly licensed users once both plans are active, within the June–September update period. Administrators are advised not to try to force updates by removing or reassigning licenses, which could lead to service or retention issues. ([cybersecuritynews.com](https://cybersecuritynews.com/microsoft-expands-mailbox-storage-50gb-to-100gb/))
Why This Matters: Mailbox storage limits have long been a pain point for organizations managing heavy email traffic—whether it’s large attachments, historical archives, or extensive correspondence. Moving to 100 GB aligns Microsoft 365’s business offerings better with enterprise expectations and helps reduce friction for businesses that hit previous caps prematurely.
What to Watch: whether Microsoft will adjust pricing or differentiate service tiers further now that basic plans offer more storage, and how this could influence competitor cloud email services. Also, whether Microsoft will revisit archive limits, compliance features, or bundle in new capabilities with the expanded mailbox quota.
