Exchange Online moves to 100 GB:
do you still need email archiving?

Updated on 17 September 2026 with the rollout complete, adding the size table by plan

In short: since 1 August 2026 the Exchange Online mailboxes of the Microsoft 365 Business plans (Basic, Standard and Premium) have grown from 50 to 100 GB. Many read this as “now I have space, I don’t need to archive email”. That is a misconception: capacity is not retention. Email archiving exists for compliant retention, legal hold, document search, immutability and recovery — none of which a bigger mailbox solves. Here is what actually changes, and what to do.

What actually changed from July 2026

The mailbox increase is not an isolated novelty: it is part of the Microsoft 365 pricing and packaging update announced for July 2026. For the Business plans (Basic, Standard and Premium) the primary mailbox of Microsoft 365 has grown from 50 to 100 GB. The enterprise plans (Office 365 and Microsoft 365 E3 and E5) were already at 100 GB and do not change; the Frontline plans do not receive the increase.

The official timing: price adjustments took effect on 1 July 2026, while the new packaging features — including the +50 GB — rolled out from June and completed on 1 August 2026, with at least 30 days notice in each tenant’s Message Center. As of September 2026 the Microsoft Learn page on Exchange Online limits lists 100 GB for all three Business suites: the rollout is complete.

Let’s be honest: it is not just free space. The update also brings price changes across several plans and new features — the Business plans gain, for instance, time-of-click anti-phishing protection for links, relevant to email security. The +50 GB is, in essence, one of the value items bundled into a broader update.

Primary mailbox and archive, plan by plan

The table summarises the limits published on Microsoft Learn in September 2026, with the rollout complete. The surprising figure is in the standalone rows: the increase applies only inside the Business suites, while Exchange Online Plan 1 bought on its own stays at 50 GB. The standalone 100 GB belongs to Plan 2.

The auto-expanding archive starts at 100 GB and grows in increments up to 1.5 TB, a figure that includes the Recoverable Items folder; shared mailboxes stay at 50 GB on all Business plans. And the same Learn page adds a prohibition that outweighs many arguments: using journaling, transport rules or auto-forwarding to copy messages into an Exchange Online mailbox for archiving purposes “is not permitted”. The big mailbox cannot become the archive, by contract.

“100 GB is enough”: the misconception

The mistake is treating the mailbox as a warehouse: as long as there is room, everything stays where it is. The inbox then becomes a de facto archive — messy, ungoverned, full of personal data and documents that nobody consciously decided to keep. Doubling the space does not solve the problem: it defers it, and in the meantime makes it bigger.

A roomy mailbox offers none of the things a company actually needs when data matters: retention rules applied automatically, a guarantee that a message cannot be altered or deleted, the ability to search and produce documents in a dispute, and selective restore of what is needed. All of this is the realm of archiving, not of space.

What email archiving actually does

Email archiving is not bigger storage: it is a system dedicated to retaining messages with characteristics the mailbox does not have.

• Governed retention — retention policies applied automatically by message category, to keep what must be kept and remove what must not be kept longer than necessary.
• Immutability — archived messages cannot be altered or deleted before their due date, not even by an administrator: a key requirement for evidentiary value.
• Legal hold and document search — the ability to freeze relevant data in a dispute (legal hold) and to search and produce it quickly (eDiscovery).
• Granular restore — recovery of a single message or of an entire mailbox, even a former employee’s, without keeping a licence active just to avoid losing the history.
• Separation from the operational mailbox — the history leaves day-to-day mail: less weight, faster searches, a clean perimeter on which to apply the rules.

When a bigger mailbox still is not enough

There is also a practical limit that often goes unnoticed: the 100 GB applies to the primary mailbox, not to the archive. On the Business Basic and Standard plans the built-in archive mailbox stays limited to 50 GB; the auto-expanding archive up to 1.5 TB is available on Business Premium and enterprise plans. In other words: the Business plans most common among SMEs gain more room in day-to-day mail, but not an archive fit for multi-year retention.

Then there is the regulatory side. There is no blanket obligation to keep all email, but when a message counts as an accounting record or commercial correspondence it falls under the ten-year retention set by the Italian Civil Code (Article 2220); tax documents and messages sent via certified email (PEC) follow their own rules; and for companies within the NIS2 perimeter, traceability and data integrity are part of the required posture. In the opposite direction, the GDPR requires not keeping personal data longer than necessary: a precise retention policy is needed, not simply more space.

How to move without being caught off guard

The arrival of 100 GB is the right moment to get organised, not to postpone. Three concrete steps: define a retention policy by data category (what to keep, for how long, what to delete); enable a managed email archiving with immutability, search and legal hold; and pair it with a backup of Microsoft 365 data, because archiving and backup address different and complementary needs.

It is also the time to review licences and migrations with retention in mind: anyone considering a cloud email migration can set up the archive and retention correctly from the start, instead of discovering the limits when a three-year-old message needs to be recovered.

AtWorkStudio has been operating from Piacenza since 2000. We are certified ISO/IEC 27001, 27017, 27018 and ISO 9001, ACN (Italian National Cybersecurity Agency) qualified for cloud services, members of Clusit (Italian Association for Information Security) and affiliated to Confindustria Piacenza in the RICT cluster.