Summary: When migrating from on-premises server to Exchange Online (Microsoft 365), you need to check the local archive mailbox size as there are archive limits on cloud tenant based on subscription plans. In this post, we will be going through the process of migrating large archive mailboxes from on premises server to Microsoft 365. We’ll also mention an EDB to PST converter tool that can help in simple and smooth migration of mailboxes to the cloud, without any size limit.
Contents
In local Exchange Server, user archives are stored on the local server instead of local PST file. This is same in Exchange Online. The only difference is that there is no archive mailbox size limit on local server, whereas there is size restriction for archive on the Exchange Online.
For Microsoft 365 Business Basic and Business Standard plans, there is a 50 GB archive limit. For the Business Premium, the maximum size limit is 1.5 TB for archive. Here?s the full list of size limits as per Microsoft 365 subscriptions:
| Subscription | Archive Limit |
| Business Basic | 50 GB |
| Business Standard | 50 GB |
| Business Premium | 1.5 TB |
| Enterprise E3 | 1.5 TB |
| Enterprise E5 | 1.5 TB |
| Enterprise E1 | 50 GB |
| Enterprise F3 | N/A |
For standalone plans, the following archive size limits will apply.
| Plan | Archive Limit |
| Exchange Online Plan 1 | 50 GB |
| Exchange Online Plan 2 | 1.5 TB |
| Exchange Online Kiosk | N/A |
So, during migration, you may face issues if your local archive is larger than the limit provided in the online tenant?s plan or subscription you have bought and provisioned for the user. Therefore, it is recommended to prepare the migration checklist beforehand to avoid any issues.
How to Migrate Large Archive Mailboxes to Microsoft 365?
You need to do some planning prior to the migration of archive mailboxes. This includes identification of the total size and item counts of each archive you want to migrate. Now depending on the size of archive, you need to apply the right license in Microsoft 365 – be it 50 GB or 1.5 TB archive plan. Although you can opt for the Premium or Enterprise subscription, you still need to do auto expansion of the archive on the online tenant as the 1.5 TB limit is not automatically allocated.
Auto expansion works as given below.
Enable Auto Expanding on Online Archives
To enable auto expanding on archives in Microsoft 365, you need to first connect to the tenant using the Exchange Online PowerShell. This is the command for the entire organization.
Set-OrganizationConfig -AutoExpandingArchive
After setting up the auto expanding archive for each and every mailbox, you need to perform the data clean-up process to remove unneeded data and large attachments, and save them in a SharePoint Online site or Microsoft Teams Site. You can also remove the data with a business retention procedure. When you reduce the amount of data to be uploaded, this ensures integrity of the mailboxes. It is suggested to retain the data on a file server as PST files are not secure and can be copied or opened in another Outlook application outside the organization.
Though the auto expanding feature is enabled, it doesn?t mean that it is expanded to the limit immediately. It will be expanded automatically bit-by-bit when the mailbox reaches a certain threshold.
Read More : How to Migrate Mailboxes over 100GB to O365?
Migrate Archive Mailboxes using Exchange Admin Center (EAC)
To migrate the mailboxes using the EAC, follow the below process:
- Log into the Exchange Admin Center (EAC).
- Click on recipients and then click on Migration.
- Click on the three dots and click on Migration Endpoints.
- Click the Add icon and then click Exchange Remote.
- Enter the email address and password.
- Provide the Remote MRSProxy Server.
- Enter the maximum number of concurrent migrations.
- Once done, click on the Add button.
- Select Remote Move.
- Click on the Add button to select the users you want to migrate.
- Enter the Exchange Administrator account.
- Select the endpoint you have just created.
- Enter the new migration batch name, select the option Move primary mailbox along with archive mailbox, and start the batch.
What to do if Archive Size is not Reduced?
If you are unable to reduce the size of the archive mailboxes, you can contact the Microsoft Premier Support with a request to increase the archive quota to import the data at once. You can increase the archive quota to 130 GB (Cloud Size), which may differ from the local size of the mailbox.
If you?re permitted and the quota is increased, you need a reliable method to move the data to the cloud as you will be working with very large mailboxes. One such method is to use an application, such as Stellar Converter for EDB. This application can migrate mailboxes from multiple Exchange Database (EDB) files with no size limit. It allows you to browse through the files and granularly export the data to Office 365 or live Exchange Server database. It can also export EDB data to PST and other file formats. The application is not limited to exporting archive mailboxes only. You can use it to export user mailboxes, disabled mailboxes, shared mailboxes, and even public folders.
