This is the first post of a two-part series about best practices and “gotchas” for migrating emails to Office 365/Exchange Online. Usually the two options that come to mind for email migration are:
- Cutover Migration
- In this approach, every mailbox and user is moved to Office 365 at once
- The challenge here is that there is downtime for emails, and in today’s connected age, it’s just not practical to take this approach
- Hybrid Migration
- This approach is the most widely-used approach
- A Hybrid Migration makes sure there is minimal to no downtime for emails
- This approach also allows migration of specific users or sets to Office 365
We’re going to focus on the more widely-used approach of a Hybrid Migration.
Benefits of Hybrid Migration
The main benefit of a Hybrid Migration is email co-existence where the Global Address List (GAL) is unified between the Cloud/Office 365 and the on-premise Hybrid Exchange Server, as well as the ability to see Free/Busy information.
Exchange Server Versions for Hybrid Exchange Migration
Exchange Server 2010 or 2013 versions will work for a Hybrid Exchange deployment. In case the on-premise version of Exchange is earlier than 2010, a free Hybrid Exchange license is available from Microsoft. This license is for Exchange Server 2010.
Key Requirements for Hybrid Migration
A key requirement for a Hybrid Exchange setup is Windows Azure Directory Synchronization, which is needed to replicate the on-premises Active Directory to Windows Azure Active Directory. The Directory Synchronization tool also has a feature called Password Synchronization which allows passwords to be synchronized between on-premises and the Cloud/Office 365.
Active Directory Federation Services (ADFS) is always the best option to federate on-premises Active Directory with the Azure Active Directory. If ADFS is already setup in your organization then there’s no need to setup Directory Synchronization. However, the Directory Synchronization tool is a quicker setup to get the Exchange migration started, and can also be added as a backup to ADFS.
Now that we’ve spelled out the differences and benefits of a Hybrid Migration, in our next post we’ll dive into some key lessons learned from a Hybrid migration to Office 365 from Exchange on-premises.