Worried Your Outlook Mailbox Is Getting Too Large?

Outlook Online Archive for Microsoft 365 Explained

When your Outlook mailbox starts getting full, it can slow things down and cause problems with sending and receiving emails. If you’re a Microsoft 365 user, there’s a straightforward solution: the Online Archive. This guide explains what it is, how it works, and how to set it up.

What Is the Online Archive?

The Online Archive is an additional mailbox that sits alongside your primary mailbox in Outlook. It’s designed specifically for storing older emails that you want to keep but don’t need to access every day.

Think of it like a filing cabinet for your email. Your primary mailbox is your desk – where you keep the things you’re actively working on. The archive is the cabinet in the corner – everything is still there and easily accessible, but it’s out of the way.

Why Would You Use It?

There are several practical reasons to use the Online Archive:

• Free up space: Your primary mailbox has a storage limit (50GB or 100GB depending on your licence). When it gets close to full, you may have issues sending or receiving emails. The archive gives you extra room without deleting anything.

• Keep everything searchable: Unlike moving emails to a local PST file, emails in the Online Archive are stored in the cloud and remain fully searchable from Outlook.

• Compliance and retention: For businesses that need to keep emails for a set period (for legal, regulatory, or internal policy reasons), the archive provides a managed way to store older messages.

• No impact on performance: A large primary mailbox can slow down Outlook, particularly for users on desktop. Moving older emails to the archive helps keep things running smoothly.

How Much Storage Do You Get?

The amount of archive storage depends on your Microsoft 365 licence:

• Exchange Online Plan 1 / Microsoft 365 Business Basic / Business Standard: 50GB archive mailbox.

• Exchange Online Plan 2 / Microsoft 365 E3 / E5 / Business Premium: Unlimited archive (auto-expanding).

For most business users on Plan 2 or above, the archive effectively has no storage ceiling. It starts at 100GB and expands automatically as needed.

How Does It Work?

The Online Archive works through retention policies and manual archiving.

Automatic Archiving (Retention Policies)

Your IT admin (or Flotek, if we manage your Microsoft 365 environment) can set up retention policies that automatically move emails older than a specified period to the archive. For example:

• Move emails older than 1 year to the archive.

• Move emails older than 2 years to the archive.

• Apply different rules to different folders.

Once configured, this runs in the background without any action needed from the user.

Manual Archiving

Users can also manually drag and drop emails or folders into the archive. This is useful if you want to tidy up specific areas of your mailbox without waiting for the automatic policy to run.

Where Do You Find the Archive?

Once enabled, the Online Archive appears as a separate mailbox in Outlook:

• Outlook Desktop (Windows/Mac): It appears in the left-hand folder pane as “Online Archive – [Your Name]”.

• Outlook on the Web (OWA): Same location – visible in the folder list.

• Outlook Mobile (iOS/Android): The archive is accessible but with limited functionality compared to desktop and web.

You can browse, search, and open archived emails just as you would with your primary mailbox.

How to Enable the Online Archive

The Online Archive needs to be enabled by an admin. Here’s how:

Option 1: Microsoft 365 Admin Centre

1. Go to admin.microsoft.com.
2. Navigate to Users > Active Users.
3. Select the user.
4. Click Mail > Manage email apps.
5. Scroll down to Archive and enable it.

Option 2: Exchange Admin Centre

1. Go to admin.exchange.microsoft.com.
2. Navigate to Recipients > Mailboxes.
3. Select the user.
4. Under Mailbox, find Archive mailbox and enable it.

If you’re a Flotek-managed client, we can enable this for you. Just raise a ticket or speak to your account manager.

Setting Up Retention Policies

To automate archiving, retention policies need to be configured. This is done through the Microsoft Purview compliance portal:

1. Go to compliance.microsoft.com.
2. Navigate to Data lifecycle management > Retention policies.
3. Create a new policy or modify an existing one.
4. Set the conditions – for example, “Move items older than 365 days to archive.”
5. Apply the policy to the relevant users or groups.

It can take up to 7 days for a new retention policy to take effect, so plan accordingly.

Important Things to Know

• The archive is cloud-only. It requires an internet connection to access. If you’re working offline, archived emails won’t be available until you reconnect.

• It’s separate from “Archive” in Outlook. The “Archive” button in Outlook (the one that appears in the ribbon) moves emails to an “Archive” folder within your primary mailbox. This is not the same as the Online Archive. The Online Archive is a completely separate mailbox.

• Deleted items in the archive follow the same retention rules. If you delete something from the archive, it goes to the Deleted Items folder within the archive mailbox.

• Search covers both mailboxes. When you search in Outlook, results can include items from both your primary mailbox and the archive.

• No shared archive. Each user’s archive is individual. There’s no option to share an archive mailbox.

Common Questions

Can I access my archive from my phone?

Yes, but with limitations. Outlook Mobile shows the archive folder, but search and browsing may be more limited than on desktop or web.

Will archiving delete my emails?

No. Archiving moves emails to the archive mailbox. They are not deleted and can be moved back at any time.

Can I archive shared mailbox emails?

Yes, the Online Archive can be enabled for shared mailboxes too, provided the shared mailbox has the appropriate licence.

What happens if I leave the company?

The archive mailbox is tied to the user’s Microsoft 365 account. If the account is deleted, the archive is also deleted (after the standard retention period). For leavers, it’s good practice to export or retain the archive before account deletion.

Is this the same as a PST file?

No. PST files are local, not searchable via Outlook’s global search, and can be lost if the device fails. The Online Archive is cloud-based, searchable, and backed up by Microsoft.

How Flotek Can Help

If your team is running into mailbox size issues, or if you want to set up automated archiving and retention policies, we can help. As part of our managed IT support, we regularly configure and manage Online Archive settings for our clients.

Whether you need the archive enabled for one user or across your entire organisation, get in touch and we’ll take care of it.

Further reading: 16 Benefits Of Microsoft 365 | What Is Microsoft Copilot

Discover how Flotek can help with our Microsoft 365 solutions.