Welcome to Email Migration Options. In this lesson, we’ll take a quick look at the two ways that you can get to Exchange Online.

The first option is Migration, which, as you would expect by the name, is the movement of user data from your source messaging system to Exchange Online. In a typical migration scenario, the organization needs, or wants, to move all existing on-prem Exchange mailboxes to Exchange Online without any need for a long-term coexistence between the on-prem Exchange org and Exchange Online. 

Coexistence is the other option for getting to Exchange Online. This term refers to a hybrid Exchange environment. In other words, when you have coexistence, you maintain both the existing on-prem messaging solution AND Exchange Online at the same time. 

While coexistence DOES offer a smoother way to move mailboxes between on-prem mail servers and Exchange Online – often without the end users even knowing it’s happening - it also requires more work for mail administrators to setup and maintain.

I should point out that when using coexistence, organizations can choose to keep some mailboxes in the on-prem messaging systems, while migrating others to Exchange Online. It’s entirely acceptable to maintain long-term coexistence if needed. In other words, coexistence isn’t just a migration strategy. It can be a long-term solution as well, if an organization needs or wants to keep some mailboxes on-prem while moving others to the cloud.

Over the next several minutes, we’re going to take a look at the specific methods for migrating from an on-prem Exchange environment to Exchange Online in Microsoft 365.