Microsoft Gives Business Users 100GB Mailboxes at No Extra Cost

Microsoft is increasing the primary Exchange Online mailbox limit from 50GB to 100GB for eligible Microsoft 365 Business customers.

The storage upgrade applies to Microsoft 365 Business Basic, Business Standard, and Business Premium. Customers do not need to switch plans or buy a separate Exchange license to get the higher limit.

Microsoft 365 Business users get another 50GB

Microsoft will keep the existing 50GB mailbox entitlement provided through BPOS_S_STANDARD.

A new EXCHANGE_STORAGE_50GB service plan adds another 50GB, bringing the primary mailbox quota to 100GB when both service plans are enabled for a user.

Microsoft is rolling out the additional service plan gradually, so some users may receive the larger mailbox before others in the same organization.

The rollout started alongside Microsoft’s 2026 Microsoft 365 packaging changes and should finish by September 2026.

Administrators do not need to enable the upgrade

Microsoft says administrators do not need to make configuration changes to receive the extra storage. Licensing updates should propagate automatically as the rollout reaches each tenant and user.

Microsoft also recommends that administrators do not remove and reassign licenses in an attempt to force the 100GB entitlement. Instead, they should allow the normal licensing rollout to complete.

However, administrator-defined mailbox quotas will remain in place. Microsoft will not automatically replace a custom limit with the new 100GB maximum.

Exchange mailbox storage does not stack

Assigning multiple Exchange licenses to one account will not combine their mailbox allowances.

Microsoft instead uses the highest mailbox storage entitlement available from a single license. For example, users cannot stack multiple 50GB entitlements to increase the quota beyond what their highest qualifying license provides.

The new Business storage entitlement also does not add extra archive capabilities.

Microsoft has made several Exchange changes recently. OWA Light is now gone following the August Exchange update, while the company has also detailed a smarter way to deploy Windows updates across organizations.