How to Migrate Archive Mailbox to Office 365?

Published By Mohit Jha

Approved By Nimisha Ramesh

Published On June 12th, 2026

Reading Time 7 Minutes Reading

The archive mailbox is Exchange’s secondary mailbox where users store their old data. If you want to migrate archive mailbox to Office 365, you can use a hybrid, PST archive file, and a professional tool to transfer on-premises archive. I will explain these methods with simple steps.

Archive mailbox is different from the primary mailbox. In Primary mailbox, user organize their day-to-day emails, contacts, calendars, etc. The archive mailbox is created to contain their old or less-used emails. The reason to use this is to reduce mailbox clutter and improve your main mailbox management.

Why Need to Migrate Archive Mailbox to Office 365?

Transferring the primary mailbox is a common task. But, there are some instances where people have to move the archive mailbox, such as these.

It is difficult to manage an on-premise archive mailbox. That’s why, to cut costs, they are moving to Microsoft 365.
Organizations moving their archive data to Office 365 help in regulatory compliance and data governance.
If you completely use the Exchange server and the local storage is full. Moving the archive helps it to reduce your server storage.
The ongoing automated retention rules tell you to move out your data.
Having your archive mailbox in Office 365 makes it easier for you to access from any device.
When an employee leaves, they have to move the complete data, including the archive mailbox.
Business is shifting from on-premise to Office 365. Then, you have to transfer all the data, including your archive data.

There can be several reasons to move your archive mailbox. To begin the process, you need to first follow the pre-migration checklist.

Preparations Before Transferring Exchange Archive Mailbox to Office 365

You cannot go straight to the methods to move your mailbox. You need to first follow this checklist.

First, check the size of the archive mailbox and count the number of items within it.
Find any unmanaged PST files in your local machines, network shared, and external drives that need to be combined.
Make sure the files in the mailbox are not corrupted. Use repair utilities to fix it.
Delete any expired, duplicate, and old data that you no longer need.
Decide on a time of migration where there is less traffic, and also contact the users about the process.
Confirm that your target Microsoft 365 has a license and contains the Exchange Online Archive feature.
Enable cloud archive mailbox for every user in the destination platform.
If your legacy archive exceeds 100 GB. Turn on the auto-expanding archive feature.
Make sure you properly check user identities and that primary SMTP addresses exactly match both source and target programs.
Check if the current mailbox is under litigation hold or legal hold. So that the strict retention rules will be carried out properly.
Assign necessary administrative roles to your migration service account.
Note down the legacy folder permissions and shared access rules, which you can later recreate.
Also, don’t forget to take a backup of your archive mailbox for security.

Once you have properly followed this checklist, you can now go through the procedure to move them.

Hybrid Migration to Migrate Archive Mailbox to Office 365

Many organizations use Hybrid migration to move their archive mailbox. This method creates a connection between on-premise to Microosft 365. This can be a lengthy process. So, I am going to divide it into a few steps. First, you must confirm your system requirements.

Make sure that your Exchange Server supports hybrid deployment.
Microsoft 365 license contains both Exchange Online and Online Archive.
Now, install and configure Azure AD Connect to sync your on-premise Active Directory with Office 365.

Configure Hybrid Configuration

With the help of the Hybrid Configuration Wizard, create a secure connection between the Exchange server and Exchange Online.

From Microsoft, download and launch the Hybrid Configuration Wizard.
Sign in to Exchange and Microsoft 365 using admin credentials.
Then, choose your hybrid deployment and configure mail flow, federation, and migration settings.
Complete your configuration.

Allow Archive Mailboxes in Microsoft 365

Run Exchange Admin Center and then go to Recipients.
Click on Mailboxes, then select the target user mailbox.
Enable Archive and wait for the archive mailbox to be provisioned.

After enabling the archive mailbox, you must create a migration batch to move your archive data. Here are the steps.

Create Migration Batch

In the Exchange Admin Center, go to Recipients and Migration.
Select Add Migration Batch, then Move to Exchange Online.
Choose users whom you want to migrate and configure migration settings and notifications.
Begin the migration batch.

You can track your process from Exchange Admin Center and complete the migration batch. Make sure you validate that the archive data is migrated successfully.

Transfer Archive Emails to Office 365 using Import PST Archive File

Some store their archive emails in PST files. With the help of the Microsoft Purview Import service, it becomes easier to upload and import PST directly to Microsfot 365 mailbox. First, locate your archive PST files, and make sure it is not password-protected. Then, assign the required permission

Log in to Microsoft Purview and go to Roles & Scopes.
Grant the Mailbox Import Export role to the admin account.
Wait for permission changes to take effect. Now, create an Import Job.
In the Microsoft Purview Compliance Portal. Navigate to Data Lifecycle Management.
Click Import and then New Import Job.
Provide a name and the Next to proceed.

Upload PST Files to your Azure Storage

First, download and install the Azure AzCopy Tool.
Copy the SAS URL and open the Command Prompt.
Run this command to upload your PST files: AzCopy.exe copy “C:\PST-Files\*.pst” “SAS-URL”
After that, create a CSV file for mapping. Include the PST file name, the user mailbox address, the target mailbox, archive mailbox option in the file and save it.
Go to the Import Job wizard and upload the CSV mapping file.
Validate Microsoft 365. Choose the data that you want to import and click submit.

Problems of Using the Above Methods

These options help you migrate your Mialbox archive to Office 365. But there is a huge risk.

Both methods are lengthy, and depending on the size of your archive mailbox and the internet. It takes a lot of time to fully migrate the mailbox.
There is always a chance that a single configuration mistake can fail the process.
You may lose your data due to synchronization issues, corrupted PST files, etc.
While migrating your archive mailbox manually, you must have the required technical expertise.

That’s why organizations always prefer a professional tool to transfer their archive mailbox to Microsoft 365.

Transfer Archive Files to Microsoft 365 Professionally

For efficient migration, tools like FreeViewer Exchange to Office 365 Migration Tool are a great option. This software easily moves your archive data from on-premise to online without any issues. It can be downloaded on Windows OS and provides a date filter to transfer specific archive emails. Here are the steps to migrate your data.

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Steps of the Professional Tool

Download your software and click Exchange server as the source and Office 365 as the destination.
Choose your data from the Workload selection and apply the date filter.
Provide the admin credentials of the Exchange Server. Press the Validate button.
Also, enter the details of Office 365, and hit Validate.
Add a user account using Fetch Users and Import Users. After that, click Start Migration.

Conclusion

Here, I have explained three ways to migrate an archive mailbox to Office 365: hybrid migration, importing a PST archive file, and using professional software. To start the process, follow the pre-migration checklist and make sure you understand the limitations of using the manual method and how professional software is a great option for businesses.