Microsoft 365 mailbox storage doubled from 50 GB to 100 GB for Business Basic, Business Standard, and Business Premium subscribers, and it is rolling out automatically through the end of September 2026. There is nothing to buy and no plan change to make. For Southwest Florida businesses that lean on email as a fallback communication channel once storms knock out phone lines, the extra headroom means fewer bounced messages right when clients, adjusters, and vendors are trying hardest to reach you.
- Primary mailboxes on Business Basic, Business Standard, and Business Premium move from 50 GB to 100 GB with no license purchase required, confirmed by Office 365 for IT Pros.
- Microsoft is delivering the increase through a new EXCHANGE_STORAGE_50GB service plan added to qualifying licenses, per Microsoft’s own Tech Community post.
- Archive mailboxes are unchanged at up to 1.5 TB with auto-expanding archiving on Business Premium; Basic and Standard still need an add-on for archiving.
- Exchange Online Plan 1 subscribers are not part of this change and stay at 50 GB.
- The rollout is gradual, so two employees on the same plan may see the new quota on different days.
What exactly changed with Microsoft 365 mailbox storage?
Microsoft is not swapping in a new plan or charging extra. It is quietly attaching a second service plan, EXCHANGE_STORAGE_50GB, to every Business Basic, Business Standard, and Business Premium license. Once Exchange Online detects that service plan on an account, it adds 50 GB to the existing 50 GB quota, bringing the total to 100 GB. Microsoft announced the change on August 19, 2026, as a follow-on to the packaging and pricing updates it rolled out July 1, and the increase is expected to reach most tenants by the end of September, according to Office 365 for IT Pros.
If your firm already reviewed its Microsoft 365 costs after the July pricing changes, this is a separate, unrelated update. We covered what actually changed with pricing and Copilot bundling in our Microsoft 365 pricing changes breakdown, and none of that affects whether you qualify for the bigger mailbox.
Why does the extra storage matter during hurricane season?
Southwest Florida offices that lose power or internet during a storm often fall back on phone data and email as the only channel that still works. Insurance claims generate long attachment-heavy threads: photos of roof damage, PDF estimates, policy documents, adjuster correspondence. A mailbox that hits its quota mid-storm bounces incoming mail without warning, which means a client’s message, or your own note to an insurer, silently fails to land. Doubling the ceiling from 50 GB to 100 GB buys real margin during the weeks when your team is least able to babysit inbox cleanup.
It also gives you more room to keep a longer local record of storm-related correspondence without immediately archiving it off to cold storage, which matters if a claim gets contested months later. We wrote about keeping communication running when storms hit in our piece on testing backups during the quiet part of hurricane season; bigger mailboxes are a small but useful piece of that same resilience picture.
Do you need to do anything to get the new quota?
No action is required for the quota itself. The service plan attaches automatically, and Microsoft has not asked admins to reassign licenses. To check whether a specific mailbox already has the new limit, an admin can open the Microsoft 365 admin center, go to the user’s mailbox settings, and look at the storage figure under Exchange properties, or run Get-Mailbox in Exchange Online PowerShell and check the ProhibitSendReceiveQuota value. If it still reads 50 GB in early October, that account has not received the new service plan yet and is worth flagging rather than assuming something is broken.
What about shared mailboxes, archives, and older plans?
Shared mailboxes inherit their quota from a licensed user’s plan the same way they always have, so a shared mailbox tied to a Business Premium license should pick up the same 100 GB ceiling as the rollout reaches that tenant. Archive mailboxes are a separate bucket and are not affected by this change at all; Business Premium already includes auto-expanding archiving up to 1.5 TB, while Basic and Standard customers who want an archive still need to add it separately. If your business runs on Exchange Online Plan 1 rather than a Business suite, this increase does not apply to you, and your primary mailbox stays at 50 GB.
Frequently asked questions
Does the mailbox storage increase cost anything extra?
No. It is included automatically for Business Basic, Business Standard, and Business Premium subscribers at no additional charge.
When will every mailbox in our tenant have the new 100 GB limit?
Microsoft began the rollout in August 2026 and expects most tenants to be covered by the end of September 2026, but individual mailboxes update on a rolling basis rather than all at once.
Does this change affect Exchange Online Plan 1 or Microsoft 365 E1?
Exchange Online Plan 1 is not included in this increase and keeps its existing 50 GB primary mailbox quota.
Do archive mailboxes also get bigger?
No. Archive mailbox limits are unchanged. Business Premium keeps auto-expanding archiving up to 1.5 TB, and Basic or Standard customers still need to add archiving separately if they want it.
If you want help checking which mailboxes in your organization have picked up the new quota, or want a broader look at how your Microsoft 365 setup would hold up during a storm, SWFIT offers a free 15-minute IT and security review. Get in touch and we will walk through your current setup with you.
