# Exchange Online Archiving Add-on: What It Adds and Which Plans Include It

> What the Exchange Online Archiving add-on adds over the included archive, which plans carry it, which need it, and the MRM retention setup that makes it work.

Canonical: https://o365hq.com/blog/exchange-online-archiving-add-on-what-it-adds-and-which-plans-include-it
Provider: IT Partner LLC — US Microsoft partner since 2006. Book: https://o365hq.com/book

Published: 2026-11-09 · IT Partner

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](/subscriptions/exchange-online-archiving-for-exchange-online) attaches to a cloud mailbox. [Exchange Online Archiving for Exchange Server](/subscriptions/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](/subscriptions/microsoft-365-business-basic), [Business Standard](/subscriptions/microsoft-365-business-standard), Office 365 E1 | Plan 1 | 50 GB | No | Add the add-on per user |
| [Microsoft 365 Business Premium](/subscriptions/microsoft-365-business-premium) | Plan 1 plus Exchange Online Archiving | Auto-expanding to 1.5 TB | Yes | Nothing to buy |
| [Microsoft 365 E3](/subscriptions/microsoft-365-e3), [E5](/subscriptions/microsoft-365-e5), Office 365 E3 and E5 | Plan 2 | Auto-expanding to 1.5 TB | Yes | Nothing to buy |
| [Exchange Online (Plan 1)](/subscriptions/exchange-online-plan-1) standalone | Plan 1 | 50 GB | No | Add the add-on, or move to Plan 2 |
| [Exchange Online (Plan 2)](/subscriptions/exchange-online-plan-2) standalone | Plan 2 | Auto-expanding to 1.5 TB | Yes | Nothing to buy |
| [Exchange Online Kiosk](/subscriptions/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](/services/microsoft-365-license-audit-optimization) checks for that. For a standalone Plan 1 user the choice is the add-on or [Exchange Online Plan 2](/subscriptions/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](/blog/exchange-online-plan-1-vs-plan-2-vs-kiosk-vs-business-basic-mailbox-licensing) 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:

1. **Enable the archive**, on the Archive page of the Purview portal or with `Enable-Mailbox <user> -Archive`.
2. **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.
3. **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`.
4. **Add personal tags** such as "Move to archive after 1 year" and "Never move to archive" for users to apply to folders.
5. **Keep the Recoverable Items tag**, which moves Recoverable Items to the archive after 14 days and keeps a held mailbox from filling its primary.
6. **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](/blog/microsoft-365-archive-mailbox-almost-full-what-to-check-and-the-options).

## 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](/services/in-place-archive-migration-microsoft-365) 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](/blog/how-to-delete-former-employees-microsoft-365-accounts-and-properly-preserve-their-mailbox-data) 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](/services/purview-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](/services/finra-sec-17a-4-compliance-microsoft-365) 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](/services/third-party-email-archive-migration-microsoft-365) 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](/blog/native-microsoft-365-backup-vs-third-party-tools).

## Sources

- Microsoft Learn, [Exchange Online Archiving service description](https://learn.microsoft.com/en-us/office365/servicedescriptions/exchange-online-archiving-service-description/exchange-online-archiving-service-description), consulted November 2026.
- Microsoft Learn, [Exchange Online limits](https://learn.microsoft.com/en-us/office365/servicedescriptions/exchange-online-service-description/exchange-online-limits), consulted November 2026.
- Microsoft Learn, [Learn about auto-expanding archiving](https://learn.microsoft.com/en-us/purview/autoexpanding-archiving), consulted November 2026.
- Microsoft Learn, [Retention tags and retention policies in Exchange Online](https://learn.microsoft.com/en-us/exchange/security-and-compliance/messaging-records-management/retention-tags-and-policies), consulted November 2026.
- Microsoft Learn, [Microsoft 365 guidance for security and compliance](https://learn.microsoft.com/en-us/office365/servicedescriptions/microsoft-365-service-descriptions/microsoft-365-tenantlevel-services-licensing-guidance/microsoft-365-security-compliance-licensing-guidance), consulted November 2026.
- Microsoft Learn, [Learn about inactive mailboxes](https://learn.microsoft.com/en-us/purview/inactive-mailboxes-in-office-365), consulted November 2026.
- Microsoft Learn, [Journaling in Exchange Online](https://learn.microsoft.com/en-us/exchange/security-and-compliance/journaling/journaling), consulted November 2026.
- IT Partner plan pages for live list prices: [Exchange Online Archiving for Exchange Online](/subscriptions/exchange-online-archiving-for-exchange-online) and [Exchange Online (Plan 2)](/subscriptions/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.

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Open the [Exchange Online Archiving for Exchange Online](/subscriptions/exchange-online-archiving-for-exchange-online) plan page for the live list price and SKU, and compare it against [Exchange Online Plan 2](/subscriptions/exchange-online-plan-2) for the users whose primary mailbox, not their archive, is the problem.