Microsoft is doubling the default primary mailbox storage in Exchange Online from 50GB to 100GB for all Microsoft 365 subscribers. The increase applies automatically to all existing and new mailboxes and requires no action from admins or users.
Rollout begins March 2026 and completes within 60 days.
What's Changing
- Default Mailbox: 50GB → 100GB
- Applies to All Microsoft 365 Plans
- No Admin Action Required
Mailbox sizes will be updated automatically. Admins can verify current mailbox quotas in the Exchange Admin Center under Recipients > Mailboxes.
Our Take
This is the right call, but Microsoft is underselling how disruptive it'll be. Users have built years of muscle memory around that Chat / Teams split — expect a wave of support tickets the week it lands. Get ahead of it with a quick communication to your users before it shows up, not after.
Bottom Line
Good change, bad rollout timing for unprepared orgs. Send a user comm now.
