Exchange online how to archive old emails

Enable the archive mailbox, then apply a retention policy that moves messages after a set age, such as about 2 or 5 years. Skip setup or verification, and mail stays in the primary mailbox, users can hit size limits, and retention rules may miss compliance requirements.

There are two separate jobs here. Manual cleanup removes mail from the primary mailbox. Automatic archiving keeps older messages searchable in the archive mailbox. If you need messages preserved, searchable, and available for compliance or eDiscovery, use the archive mailbox. If you need messages deleted after a period, use retention to delete them instead.

How do you archive old emails?

Manual archiving versus automatic archiving

Manual archiving is a user action, usually moving messages out of the primary mailbox. Automatic archiving is policy-driven and starts after the archive mailbox exists. That difference matters because retention can move mail into the archive, but it can also delete mail without creating an archive target first.

Suppose a user wants to keep invoices older than about 3 years but delete daily junk after about 90 days. Put the invoices in the archive mailbox and apply a delete rule to the junk. One mailbox can have both behaviors, but the policy must target the right scope.

📊 Plan 1 can automatically move old messages to an In-Place Archive. Source: Microsoft.

What you'll need before you start

• An Exchange admin account with permission to manage mailboxes in the Exchange admin center.
• The user’s primary SMTP address or mailbox name.
• Confirmation that the mailbox is licensed for Exchange Online archiving.
• A retention rule or folder plan if old mail should move automatically.
• Access to Outlook and Outlook on the web for verification.

Archive setup checklist

How do you turn on the archive mailbox?

Open the Exchange admin center, select the user’s mailbox, and enable the archive mailbox there. After provisioning finishes, the archive should appear in both Outlook and Outlook on the web. If it does not appear right away, have the user sign out and sign back in so the folder tree refreshes.

1. Sign in to the Exchange admin center.
2. Go to Recipients > Mailboxes.
3. Select the user’s mailbox.
4. Open the mailbox settings and choose the archive option.
5. Turn on the archive mailbox and save the change.
6. Wait for provisioning to finish, then confirm the archive is listed in the mailbox details.
7. Ask the user to reopen Outlook or sign in to Outlook on the web.

Exchange Online archiving is a cloud-based archiving service managed from the Exchange admin center. It supports compliance and eDiscovery, and it is available as an add-on for online mailboxes. Archived mail stays accessible in Outlook and Outlook on the web, so users do not need local PST files to keep older content.

How do you move old mail automatically?

Use a retention policy or retention tag to move older messages into the archive mailbox after a set age. That works best when you want mailbox content organized automatically, not when you want users to drag folders by hand. The archive mailbox must exist before the policy can move mail there.

1. Set the action to move to archive or delete, depending on the outcome you need.
2. Choose the age threshold, such as 2 years or 5 years.
3. Scope the rule to the mailbox, folder, or message class you want.
4. Save the rule and assign it to the target mailbox.
5. Verify that the archive mailbox already exists before expecting movement.

Retention policies and archive mailboxes work alongside each other. A policy can move older items into the archive, while a separate rule can delete content after a different period. If you need only certain folders archived, target those folders directly instead of applying a mailbox-wide rule.

A common first-timer mistake is applying an age rule to the whole mailbox when only one folder should move. Suppose a finance mailbox keeps statements in one folder and meeting notes in another. Set the archive rule on the statements folder only, then confirm the notes stay in the primary mailbox.

What differs between age-based and folder-based archiving?

Age-based archiving is better when every message older than a set period should move. Folder-based archiving is better when only part of the mailbox should move. Use folder scope when users have a clear filing system, and use mailbox scope when the rule should cover everything.

Why can users not see archived mail?

Users often think mail is missing when the archive mailbox exists but Outlook is still showing cached data, the archive was not provisioned correctly, or they are checking only the primary mailbox. Outlook on the web is the best first check because it reflects server-side state without local sync limits.

1. Open Outlook on the web and confirm the archive mailbox appears there.
2. In Outlook desktop, check File > Account Settings > Account Settings > Change > More Settings and review cached mode settings.
3. Check whether Outlook is set to keep only a limited amount of mail offline.
4. Confirm the archive mailbox is enabled in the Exchange admin center for that user.
5. Sign out of Outlook, reopen it, and force a folder refresh.

Outlook cache mode can hide older messages locally after a default period. NAKIVO notes the default local retention is one year, so older mail may exist on the server but not in the local cache. That is a client setting, not proof that the archive mailbox is empty.

Exchange Online Plan 1 does not include a standard archive mailbox by default. Exchange Online Archiving adds a 50 GB archive mailbox per subscriber, and some subscriptions automatically get additional archive storage. Exchange Online Plan 2 includes a 100 GB primary mailbox and a 100 GB archive mailbox, with auto-expanding archiving available up to about 1.5 TB for eligible setups and built-in data loss prevention.

If the archive appears in Outlook on the web but not in Outlook desktop, fix the client first. Change cached mode settings, then reopen the profile. If the archive still does not appear, check licensing and verify that the archive mailbox exists in the Exchange admin center before changing anything else.

What happens when the archive mailbox fills up?

When the archive reaches its included limit, expansion depends on the license and the setup. Some subscriptions automatically get more archive storage, and eligible environments can use auto-expanding archiving. If the archive is not eligible for expansion, you need to review licensing or reduce stored content.

Exchange Online Plan 2 provides a 100 GB archive mailbox, with auto-expanding archiving available up to 1.5 TB for eligible setups. Exchange Online Archiving includes a 50 GB archive mailbox per subscriber. Plan selection should happen before deployment, because the right choice depends on how much mail you need to retain and whether compliance requires long-term preservation. (Microsoft)

Archived mail remains searchable and accessible through supported clients after it leaves the primary mailbox. That is one reason local PST files are less desirable: they are harder to manage centrally, harder to govern for compliance, and easier for users to misplace.

Common mistakes

• Assuming retention creates an archive mailbox automatically. It does not.
• Assuming Plan 1 includes a built-in archive mailbox. It usually needs Exchange Online Archiving or another qualifying license.
• Assuming Plan 2 always means 1.5 TB of archive space. The 1.5 TB figure applies to auto-expanding archiving in eligible setups.
• Checking only Outlook desktop when Outlook on the web already shows the archive.
• Using PST export as the default archive method instead of a managed archive mailbox.
• Skipping cached mode checks when older mail is visible online but not locally.

Microsoft says Exchange Online supports a custom domain for business email, but that does not change archive behavior. Domain setup and archive setup are separate tasks. Configure the mailbox, license, and retention rule first, then verify access in both Outlook and Outlook on the web.

Frequently asked questions

How do I archive old emails in Exchange Online?

Enable the archive mailbox in the Exchange admin center, then assign a retention policy or tag that moves older mail after the age you choose. If you only need cleanup, you can move or delete items manually, but that does not replace a managed archive.

How do I turn on an archive mailbox in Exchange Online?

Use Exchange admin center > Recipients > Mailboxes, select the user, and enable the archive mailbox from the mailbox settings. After provisioning, check Outlook on the web first. If the archive exists there but not in Outlook desktop, review cached mode and reopen the profile.

What’s the difference between the primary mailbox and the archive mailbox?

The primary mailbox is where current mail lives. The archive mailbox is a separate, online store for older mail that should stay searchable but no longer needs to sit in the main mailbox. Retention can move items between them without changing the message itself.

How much archive storage does Exchange Online include?

Exchange Online Archiving includes a 50 GB archive mailbox per subscriber. Exchange Online Plan 2 includes a 100 GB archive mailbox, and eligible setups can use auto-expanding archiving up to about 1.5 TB. Plan 1 needs an archive add-on or a qualifying license for archive mailbox use.

Can users access archived email in Outlook and Outlook on the web?

Yes. Archived mail is available in Outlook and Outlook on the web, which makes it searchable and reachable from supported clients. If users cannot see it, check provisioning, license assignment, and cached mode before assuming the archive is missing.

How do retention policies move old messages into the archive?

Assign a retention rule that uses an age threshold and the action move to archive. Apply it to the correct mailbox or folder scope, then confirm the archive mailbox already exists. If you want deletion instead, use a delete action rather than an archive action.