Migration from an on-premises Exchange Server to Office 365 is a strategic move for companies as the latter offers collaboration, co-authoring, flexibility, scalability, and various other benefits and features. But migration is a very delicate process. It sometimes becomes a daunting task for the administrators if there are any technical hiccups, planning issues, communication errors, and data validation problems. In this article, we will talk about some common issues that may arise during on-premises Exchange to Office 365 migration and see how to fix them. We will also mention a third-party Exchange migration tool that can reduce the manual work and simplify the process when it comes to migration of data.
Common Issues during On-premises Exchange to Office 365 Migration
Below, we will be discussing some common issues that you may encounter during Exchange Server to Office 365 migration.
1. Mailbox Move Failure
In a minimal or full hybrid setup, you may face a situation where the migration batch fails, leading to unsynchronized mailboxes. You might also get an error message, saying “Mailbox not found.” This could happen for various reasons, such as:
- MRSProxy service is either not working or disabled.
- Misconfiguration in the local Exchange Server.
- Exchange GUID in the local Exchange Server doesn’t match the cloud identity.
- Authentication issues or missing permissions.
To fix the issue, you can do the following:
- Enable the MRSProxy and review the configuration on the Client Access Server (CAS).
- Check for any updates or Cumulative Updates (CU) on the local Exchange Server.
- Check the Exchange GUID and match it with the cloud identity.
- Run the Test-MRSHealth command to check the mailbox replication service status.
2. Missing Data during Migration
Another common issue that you may encounter is missing data during migration. Here are the possible reasons for this:
- Migration of data during peak hours.
- Internet or network bandwidth is saturated.
- Low internet bandwidth.
- Large mailboxes.
- Throttling of connection from Microsoft.
Possible fixes to the issue include:
- Analyze the internet connection, mainly the upload speed and optimize the connection.
- You can use the ExpressRoute from Microsoft, but this would be costly.
- You can use the drive shipping method where large PST files can be saved in an encrypted drive and shipped to Microsoft for import.
- Pause any antivirus or backup solution during the transfer.
- Make sure that the data is transferred during off-peak hours.
3. Authentication and Synchronization Issues
When moving data from a local Exchange Server using the Hybrid method, you need to setup the Entra AD Connect to synchronize the local identities with the cloud. You may encounter a situation where the credentials do not match or the users are not able to log in to their Office 365 account. This could happen due to:
- Entra AD Connect synchronization issues.
- Duplicate or missing SMTP Addresses or UPN suffix.
- Incorrect license assigned.
In this case, you can try the following fixes:
- Review the logs and configuration of the Entra AD Connect.
- Assign or review the Microsoft 365 license assigned to the users.
- Check the UPN Suffix of the user, along with the Proxy Address in the local AD properties.
4. Retention of Data and Size Issues
Office 365 has mailbox size limitations, depending on the license. The Office 365 Business Standard has a 50 GB mailbox limit and the Office 365 Enterprise E3 has 100 GB size limit. If the local mailboxes exceed this limit, it will stop the migration. Although you can create retention policies to move data to the Online Archive depending on the date, this will still halt the migration. When you continue the process again, the migration of data would be inconsistent.
This can be resolved by going through a cleanup process post-migration to Office 365. You need to ensure that the data is migrated within the mailbox size limits on the cloud.
5. Migration Endpoint Issues
When creating a migration endpoint, it may fail and consequently the migration batches will not start due to the following:
- Misconfiguration in the endpoint creation.
- Incorrect or expired credentials.
- Network limitations or blocked ports.
Possible solutions to the problem include:
- Try to recreate the endpoint from the Exchange Admin Center (EAC).
- Test the administrator credentials to ensure that they are working.
- Make sure the credential format is Domain\Username.
- Check with the network administrators that ports 443 and 80 are open.
- Confirm that the SSL certificate is valid and is from a certificate authority.
Use a Specialized Exchange Migration Tool for Data Migration
To avoid issues during data migration, you can take the help of specialized Exchange migration tool. Stellar Migrator for Exchange is one such tool that offers an intuitive and simple interface that helps in smooth and safe migration of data. This tool provides the below migration options:
- Local Exchange Server to Local Exchange Server
- Local Exchange Server to Office 365
- Office 365 to Local Exchange Server
- Office 365 to Office 365
The tool offers features such as automatic mapping of mailboxes from source to destination, parallel exports, and priority exports. It is compatible with Exchange Server 2010 till 2019.
Conclusion
As you have seen, there are various issues that may occur during local Exchange Server to Office 365 migration. Therefore, you should plan the migration well. Before migration, you should do data analysis, check mailboxes size, the licenses to be assigned, and prepare the local Exchange Server for the migration. Data sanitization is important to be done before starting the migration. You can also keep an Exchange migration tool, such as Stellar Migrator for Exchange, in hand. This tool can directly migrate data from local Exchange Server to Office 365 with complete integrity.
Learn more about how to simplify your On-Premises Exchange migration and avoid common pitfalls at the Stellar Data Recovery website.
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