Microsoft 365 Is Doubling Mailbox Storage: What the Move from 50GB to 100GB Means for Your Business
If you’ve ever gotten that dreaded “mailbox almost full” warning in Outlook, there’s good news on the way. As part of its broader 2026 pricing and packaging update, Microsoft is doubling the primary mailbox storage for Microsoft 365 Business Basic, Business Standard, and Business Premium from 50GB up to 100GB per user.
It’s one of the more welcome changes in an update that also brings price increases to several plans, so it’s worth understanding exactly what’s changing, when it lands, and what it means for your organisation.
What’s Actually Changing
Today, Microsoft 365 Business Basic, Standard, and Premium each include a 50GB primary Exchange Online mailbox per licensed user. Once the update rolls out, that limit rises to 100GB — no extra purchase, no separate add-on, and no need to enable an archive mailbox just to buy yourself breathing room.
This has historically been a pain point for growing businesses. A 50GB limit sounds generous until you have a handful of users with years of email history, large attachments, or heavy CC habits. Many organizations ended up paying for Exchange Online Plan 2 or upgrading to an E3/E5 plan purely to unlock the larger 100GB mailbox — even if they didn’t need any of the other enterprise features that come with those tiers. This change removes that specific reason to upgrade.
Rollout Timeline
This isn’t an instant, flip-the-switch change for every tenant on day one.
Here’s the general timeline Microsoft has communicated:
- Packaging updates (including the mailbox increase) began rolling out in June 2026
- Rollout is expected to be substantially complete by August 1, 2026, though Microsoft has since indicated that backfill for Business SKUs specifically may extend to September 30, 2026
- Pricing updates take effect separately, from July 1, 2026
- Tenants receive at least 30 days’ notice via the Microsoft 365 Message Center before the change becomes visible in their environment
In other words: don’t assume every mailbox in your tenant will show 100GB the moment you read this. Check your Message Center for tenant-specific timing, and keep an eye on actual mailbox usage in the admin center in the meantime.
Why This Matters if You’re Close to the Limit
If you have users sitting near the current 50GB ceiling, this update can’t come soon enough. Under existing Exchange Online thresholds, mail flow starts getting restricted well before a mailbox technically “fills up”:
- Around 49GB, users get a warning that they’re approaching the limit
- Around 49.5GB, users may be blocked from sending new mail
- At 50GB, the mailbox can be blocked from sending and receiving, with incoming messages bounced back to senders
A user sitting at 48GB today is using about 96% of their available space. Once the same mailbox moves to a 100GB limit, that usage drops to roughly 48% — a meaningful difference that buys time before you need to think about archiving, cleanup policies, or third-party storage tools.
That said, more storage isn’t a substitute for good hygiene. Duplicated attachments, old newsletters, and years of untouched mail will still slow down search and sync in Outlook, even with double the ceiling.
The Bigger Picture: Pricing Changes Alongside the Storage Boost
The mailbox increase doesn’t exist in isolation — it’s part of a wider set of 2026 changes to Microsoft 365 commercial pricing and packaging, and the details vary by plan:
- Business Basic and Business Standard are both seeing list price increases (commonly cited in the range of roughly 12–17%, depending on region and reporting)
- Business Premium is notably not increasing in price, while still receiving the same 100GB mailbox bump plus additional security features (Microsoft Defender for Office 365 Plan 1, Intune capabilities, Conditional Access, and more)
- Existing customers keep their current pricing until their next renewal after July 1, 2026
That combination — Premium holding its price while Standard rises — narrows the practical cost gap between the two tiers. For organizations already weighing whether to add security tooling on top of Standard, this update makes stepping up to Premium a more straightforward decision than it was a year ago.
Beyond storage and pricing, the same update also introduces enhanced Copilot Chat with admin controls, URL time-of-click protection for links in email, and various Intune device-management improvements — though these arrive at different points across the plan lineup.
What Businesses Should Do Now
- Check your Message Center. Look for the notification (referenced internally as part of the “2026 Microsoft 365 Packaging Update”) for your tenant’s specific rollout window.
- Audit mailboxes that are close to 50GB. Even with the increase coming, users near the limit could still hit sending restrictions before the update reaches your tenant.
- Revisit any workarounds you’ve already paid for. If you upgraded specific users to Exchange Online Plan 2 or an E3/E5 license purely for the 100GB mailbox, it may be worth reassessing whether that’s still necessary once Business Basic or Standard includes the same limit.
- Factor the price changes into your renewal timing. If you’re close to a renewal date, understand whether you’ll renew before or after July 1, 2026, since that determines which pricing applies.
- Reconsider Business Premium if you’re on Standard. With the price gap narrowing and both tiers getting the same mailbox increase, Premium’s added security features may now be more cost-effective than before.
The Bottom Line
Doubling mailbox storage from 50GB to 100GB is a genuinely useful change for any business that’s been fighting mailbox limits — and it removes one of the more common reasons organizations felt pressured into buying enterprise-tier licensing they didn’t otherwise need. Just don’t expect it to appear in your tenant overnight; treat the Message Center as your source of truth for exact timing, and use the extra space as an opportunity to review your broader Microsoft 365 licensing rather than just breathing a sigh of relief and moving on.
