When migrating mailboxes from on-premises Exchange Server to Exchange Online in a hybrid setup, you may notice that the migration process has failed. An error message "AdminLimitExceededException" may appear. This might happen during the migration of the last few mailboxes.
The error indicates that the admin limit has been exceeded at the destination. This could be a factory limit on the size, or number of items, or any other manual limit you might have added as a custom limit on the destination.
Let’s see how to fix this error and migrate mailboxes without any issues.
Solution For "AdminLimitExceededException" Error
You need to first understand what is different between the mailboxes that have been migrated without any issues and the ones that are failing. This will give you a clear picture of the issue.
You can check if the error is only on a particular mailbox/s. For this, you can create a new user with a mailbox and try to migrate the mailbox to Exchange Online. This will help you to determine if it is a server-related issue or just related to the particular mailbox. You can also try to migrate the mailbox, which has an issue, without any other mailbox.
Since the Entra ID Connect also synchronizes some of the user’s Active Directory attributes, you need to check if there are any issues or warning in the Entra ID synchronization.
If not, then it is suggested to run the full synchronization and full import of both the connectors. Follow these steps:
- Click on Connectors.
- Right-click on the Active Directory Domain Services connector and click on Run.
- Click on Full Import.
- Once it is complete, run the Full Synchronization.
When this is complete, you need to run Full Import and Full Synchronization on the Windows Azure Active Directory Connector. This will refresh the connectors’ data.
After this is complete, you need to check if there are any issues in the Synchronization Server Manager. If there are no visible issues, you can retry the migration.
Another option is to check the Active Directory Schema objects of the users in question. You can investigate the Global Address List attribute of the user or object. It might happen that the Global Address List has reached its limit, leading to the Admin Limit Exceeded error. The possible solution is to remove some of the values from the Global Address List and run the setup of Exchange Server with the /PrepareAD parameter.
Although this operation will not incur data loss, it is suggested to take a backup before modifying anything on the server.
After the operation is complete, try to migrate the mailboxes again.
An Alternative Solution to Migrate Mailboxes
For hassle-free migration of mailboxes, you can take the help of third-party EDB to PST converter tools, like Stellar Converter for EDB. This tool can easily migrate data from Exchange Server database to a newer Exchange Server or Exchange Online. It allows the admins to open live database (without unmounting it) or standalone database (just the EDB file without a live Exchange Server). The tool has an Outlook like interface and allows to granularly export user mailboxes, user archives, shared mailboxes, disabled mailboxes, and even public folders. With the tool, you can also save EDB data to PST and other file formats. It offers features, like automatic mailbox matching, priority exports for VIP users or resources, and parallel exports.
Conclusion
The AdminLimitExceededException error can hinder your migration process. Above, we have mentioned some possible solutions to fix the error. To avoid issues during data migration, you can use an EDB converter tool, like Stellar Converter for EDB. The tool allows you to export mailboxes and other data from your Exchange Server database file to Exchange Online with complete integrity. The tool supports EDB files created in Exchange Server 2019, 2016, 2013, 2010, and earlier versions.
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