Knowledge Base

Microsoft 365 Email Archiving – Complete Setup Guide

Microsoft 365 Email Archiving – Complete Setup Guide (Knowledgebase Format)

This guide explains how to enable and configure Microsoft 365 Email Archiving, including Online Archive Mailboxes, Auto‑Expanding Archive, and Retention Policies.

 Overview

Microsoft 365 provides built‑in archiving features that help organizations store older emails securely and reduce mailbox size. Archiving includes:

• In‑Place Archive (Online Archive Mailbox)
• Auto‑Expanding Archive (Unlimited Storage)
• Retention Policies to automatically move old emails
• Litigation Hold for compliance and legal protection

This article explains how to enable and configure each feature.

 Prerequisites

Before enabling archiving, ensure:

• You have Microsoft 365 Business Premium, E3, E5, or Exchange Online Plan 2
• You are a Global Admin or Compliance Admin
• The user mailbox is active and licensed

1. Enable Archive Mailbox (Online Archive)

The Online Archive mailbox provides additional storage for older emails.

Steps

1. Sign in to Microsoft 365 Compliance Center
   https://compliance.microsoft.com
2. Go to Data Lifecycle Management → Archive
3. You will see a list of users
4. Select the user you want to enable archiving for
5. Click Enable Archive
6. Wait 5–10 minutes for provisioning

Result

A new mailbox called Online Archive – user@domain.com appears in Outlook and Outlook Web.

2. Enable Auto‑Expanding Archive (Unlimited Storage)

Auto‑expanding archive increases archive capacity automatically beyond 100GB.

Steps

1. Go to Compliance Center
2. Navigate to Data Lifecycle Management → Archive
3. Click Settings
4. Enable Auto‑expanding archive

Result

Microsoft automatically adds additional archive space as needed.

3. Create Retention Policy to Move Old Emails to Archive

Retention policies automatically move emails older than a specific age (e.g., 1 year) to the archive mailbox.

Steps

1. Open Compliance Center
2. Go to Data Lifecycle Management → Microsoft 365 retention
3. Click Create retention policy
4. Enter a name (Example: Move emails older than 1 year)
5. Choose Retention settings:
• Retain items for: 1 year
• Action: Move to archive
6. Choose locations:
• Enable Exchange email
7. Assign the policy to:
• All users
• Or specific users
8. Save and publish the policy

Result

Emails older than the defined period automatically move to the archive mailbox.

4. Enable Litigation Hold (Optional)

Litigation Hold preserves all mailbox content, including deleted items.

Steps

1. Go to Microsoft 365 Admin Center
2. Open Active Users
3. Select the user
4. Go to Mail → Manage Litigation Hold
5. Enable Litigation Hold
6. Set a duration (or leave unlimited)
7. Save changes

Result

All emails are preserved for legal compliance.

5. How Users Access the Archive

Outlook Desktop

• Appears as Online Archive – user@domain.com

Outlook Web

• Appears under folder list as Archive Mailbox

Users can drag and drop emails or rely on retention policies.

 6. Verify Archive Status

To confirm archiving is enabled:

Using Compliance Center

• Go to Archive
• Check the Status column (Enabled/Disabled)

Using PowerShell (Optional)

Get-Mailbox -Identity user@domain.com | Select ArchiveStatus

7. Common Issues & Solutions

Conclusion

Microsoft 365 archiving is a powerful tool for managing mailbox size, ensuring compliance, and storing long‑term email data. By enabling Online Archive, Auto‑Expanding Archive, and Retention Policies, your organization can maintain clean, efficient mailboxes with unlimited storage.