Exchange Online Archiving Add-on: What It Adds and Which Plans Include It
Every Exchange Online mailbox above Kiosk already comes with an archive, so the Exchange Online Archiving add-on is not what gives you one. What it buys is three things a Plan 1 mailbox lacks: an archive that grows past 50 GB toward 1.5 TB, the right to place a litigation hold, and, in its Exchange Server edition, a cloud archive for a mailbox that still lives on premises. This article separates the archive from the add-on, lists which plans already carry it, and covers the retention setup without which an archive does no work at all.
Archive mailbox basics versus the add-on
An archive mailbox is a second mailbox attached to a user's primary, with its own quota and its own folder tree in Outlook. Content search and eDiscovery cover it as they cover the primary.
What a mailbox gets without the add-on depends on the Exchange Online plan under the license:
- Exchange Online Kiosk (Microsoft 365 F3, Office 365 F3): a 2 GB mailbox, no archive, and the add-on cannot be attached.
- Exchange Online Plan 1 (Business Basic, Business Standard, Office 365 E1): a 50 GB primary and an archive capped at 50 GB. No litigation hold.
- Exchange Online Plan 2 (Microsoft 365 E3 and E5, Office 365 E3 and E5): a 100 GB primary, an archive that starts at 100 GB and auto-expands toward 1.5 TB, and litigation hold.
The add-on gives a Plan 1 mailbox the Plan 2 archive behavior without touching the primary: a 100 GB archive that auto-expanding archiving can take to 1.5 TB, litigation hold, and the larger Recoverable Items quota a hold needs. It comes in two editions. Exchange Online Archiving for Exchange Online attaches to a cloud mailbox. Exchange Online Archiving for Exchange Server attaches to a mailbox that stays on an on-premises Exchange server in a hybrid configuration, with the archive in Exchange Online and Outlook opening both. The live list price of each edition is on its plan page.
Which plans already include it, and which need the add-on
| Plan | Exchange plan inside | Archive without the add-on | Litigation hold | What to do |
|---|---|---|---|---|
| Business Basic, Business Standard, Office 365 E1 | Plan 1 | 50 GB | No | Add the add-on per user |
| Microsoft 365 Business Premium | Plan 1 plus Exchange Online Archiving | Auto-expanding to 1.5 TB | Yes | Nothing to buy |
| Microsoft 365 E3, E5, Office 365 E3 and E5 | Plan 2 | Auto-expanding to 1.5 TB | Yes | Nothing to buy |
| Exchange Online (Plan 1) standalone | Plan 1 | 50 GB | No | Add the add-on, or move to Plan 2 |
| Exchange Online (Plan 2) standalone | Plan 2 | Auto-expanding to 1.5 TB | Yes | Nothing to buy |
| Exchange Online Kiosk, Microsoft 365 F3, Office 365 F3 | Kiosk | None | No | Not supported; move the user to Plan 1 or higher |
Three things follow. Business Premium already includes the add-on, so a Business Premium tenant paying for it on the same users pays twice; the license audit checks for that. For a standalone Plan 1 user the choice is the add-on or Exchange Online Plan 2: the add-on keeps the 50 GB primary, Plan 2 doubles it to 100 GB, and both prices are on the plan pages. And it is per user: twelve people whose mail volume or legal exposure justifies it, not the other two hundred.
One 2026 note: Microsoft's February 2026 packaging announcement added 50 GB of email to the Business plans from 1 July 2026; check the Exchange Online limits page before quoting a size, as our Plan 1 versus Plan 2 comparison explains.
The retention policy and MRM setup that makes the archive useful
Buying the add-on does nothing by itself. Items reach the archive two ways: a user drags them there, or a messaging records management (MRM) retention tag moves them. Only MRM moves mail to the archive; Microsoft Purview retention policies retain and delete but never relocate items.
The sequence that works:
- Enable the archive, on the Archive page of the Purview portal or with
Enable-Mailbox <user> -Archive. - Read the Default MRM Policy. Every new mailbox gets it, and its "Default 2 year move to archive" tag starts moving items older than two years once an archive exists.
- Decide the age. Two years is a default, not a rule; a mailbox that reaches 50 GB in eighteen months needs a one-year tag. Create a tag with the chosen age and swap it in, or assign a policy of your own with
Set-Mailbox -RetentionPolicy. - Add personal tags such as "Move to archive after 1 year" and "Never move to archive" for users to apply to folders.
- Keep the Recoverable Items tag, which moves Recoverable Items to the archive after 14 days and keeps a held mailbox from filling its primary.
- Turn on auto-expanding archiving with
Set-OrganizationConfig -AutoExpandingArchive. It cannot be turned off once on, and Microsoft caps growth at about 1 GB a day, so it will not absorb a PST import over a weekend.
The Managed Folder Assistant visits each mailbox at least once every seven days; Start-ManagedFolderAssistant <user> forces it. When the archive itself fills, see our archive mailbox almost full article.
The 100 GB primary and the growth problem
The add-on does nothing for the primary. A Plan 1 primary stays at 50 GB with or without it, a Plan 2 primary is 100 GB, and no license or setting takes a primary past 100 GB. A 95 GB mailbox with a two-year tag and 60 GB of mail younger than two years fills within months; the fix is a shorter tag age, not a bigger mailbox.
Two practical points. Outlook desktop caches the primary and treats the archive as online-only, so mail that moves there stops being searchable offline; set the age with that in mind. A shared mailbox needs no license up to 50 GB with no archive and no hold; once it needs either, it needs its own Plan 2 or Plan 1 plus add-on license. Auto-expanded storage has limits of its own: the auxiliary folders do not open in Outlook mobile, and moving one between tenants is slow, as the In-Place Archive Migration page explains.
Holds, eDiscovery and the Recoverable Items folder
Litigation hold is the second thing the add-on buys: deleted and edited items stay in the Recoverable Items folder past the normal window, invisible to the user and searchable by an eDiscovery manager. Without Plan 2 or the add-on the option is not available, and Microsoft's licensing guidance ties Purview retention for Exchange content to the same plans.
- Recoverable Items quota. 30 GB by default, 100 GB under a hold; on a held mailbox with an archive, the 14-day MRM tag moves that content to the archive.
- Former employees. A held mailbox whose license is removed becomes an inactive mailbox and keeps its content without a license, provided the hold or a Purview retention policy was in place first. Assign the add-on or Plan 2 before offboarding; our former employee mailbox guide covers the order.
- eDiscovery. Content search covers primaries and archives on every plan. Case-based eDiscovery (Standard) is listed for Exchange Online Plan 2, Microsoft 365 E3 and Business Premium in Microsoft's licensing guidance; eDiscovery (Premium) needs Microsoft 365 E5 or E5 Compliance. The eDiscovery search assistance service runs a search and export when no one in-house has done one.
When a third-party archive still makes sense
The add-on or Plan 2 covers the storage and hold problem for most 20 to 500 person organizations. Four situations still call for an archive outside the tenant:
- Regulatory journaling. Broker-dealers under SEC Rule 17a-4 and FINRA rules need a journal copy of every message in write-once storage with supervisory review. Exchange Online journals to an external address, not to a mailbox in the same tenant, and an archive mailbox is not a journaling target. The FINRA and SEC 17a-4 compliance service maps the rule to the tenant.
- Independence from the tenant. A hold set by a Global Administrator can be removed by one. Where the board or the insurer wants a copy no one in the tenant can delete, it lives elsewhere.
- Multi-channel capture. Text messages, Bloomberg, Slack and a prior Google Workspace estate under one retention schedule.
- A legacy archive you already pay for. Mimecast, Proofpoint, Barracuda and Global Relay archives hold years of mail that predate the tenant; bringing it in is the project on the third-party archive migration page.
If none of the four applies, the add-on or Plan 2 plus a working MRM policy is the simpler answer.
Frequently asked questions
Does Exchange Online Plan 1 include an archive mailbox?
Yes, up to 50 GB. Auto-expanding archiving and litigation hold come with the Exchange Online Archiving add-on or with Exchange Online Plan 2.
Is Exchange Online Archiving included in Microsoft 365 Business Premium?
Yes, so its users get the auto-expanding archive and litigation hold with nothing added. Business Basic and Business Standard carry Plan 1 and need the add-on per user.
Can I add Exchange Online Archiving to a Kiosk or F3 mailbox?
No. Kiosk mailboxes have no archive and cannot take the add-on. A frontline user who needs an archive or a hold moves to Plan 1 plus the add-on, or to Plan 2.
Is an archive mailbox a backup?
No. It sits in the same tenant under the same administrators. A hold preserves content against deletion; a point-in-time restore needs a backup product, compared in our native backup versus third-party tools article.
Sources
- Microsoft Learn, Exchange Online Archiving service description, consulted November 2026.
- Microsoft Learn, Exchange Online limits, consulted November 2026.
- Microsoft Learn, Learn about auto-expanding archiving, consulted November 2026.
- Microsoft Learn, Retention tags and retention policies in Exchange Online, consulted November 2026.
- Microsoft Learn, Microsoft 365 guidance for security and compliance, consulted November 2026.
- Microsoft Learn, Learn about inactive mailboxes, consulted November 2026.
- Microsoft Learn, Journaling in Exchange Online, consulted November 2026.
- IT Partner plan pages for live list prices: Exchange Online Archiving for Exchange Online and Exchange Online (Plan 2).
Key takeaways
- Exchange Online Plan 1 already includes a 50 GB archive; the Exchange Online Archiving add-on adds auto-expanding archiving toward 1.5 TB, litigation hold and the larger Recoverable Items quota a hold needs. It does not enlarge the primary mailbox.
- Exchange Online Plan 2, Microsoft 365 E3 and E5, Office 365 E3 and E5 and Microsoft 365 Business Premium already carry the add-on's capabilities; Business Basic, Business Standard, Office 365 E1 and standalone Plan 1 need it per user; Kiosk and F3 mailboxes cannot take it.
- An archive does no work until it is enabled and a messaging records management tag moves mail into it; Purview retention policies retain and delete but never move items to the archive.
- No license takes a primary past 100 GB; the fix for a growing primary is a shorter move-to-archive tag age, and a shared mailbox needs its own license once it needs an archive beyond 50 GB or a hold.
- A third-party archive still makes sense for regulatory journaling under SEC Rule 17a-4, for a copy independent of tenant administrators, for multi-channel capture, or when a legacy archive already holds years of mail.
Open the Exchange Online Archiving for Exchange Online plan page for the live list price and SKU, and compare it against Exchange Online Plan 2 for the users whose primary mailbox, not their archive, is the problem.
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