Office 365 supports a variety of migration methods that customers can use. The choice of migration method can be influenced by a wide range of factors such as the number of objects involved in the migration, the amount of data to be moved to Office 365, the version of Exchange Server (if any) running on-premises, long-term migration or co-existence requirements, whether the organization uses non-Exchange email servers, and even the budget available to spend on the migration project.

The migration methods that are available are:

Cutover migration

Staged migration

Hybrid configuration

IMAP migration

Third party migration tools

The best place to start is with the business requirements of the migration project. The business requirements should include factors such as the need to complete the migration by a particular date, whether a back-out option for the migration needs to be included, or whether some email resources will remain on-premises. As you will see when you read through this chapter, each migration method has different benefits and constraints, and they may not all suit the business requirements of the project.

The next items to consider are the technical requirements, as they will often quickly eliminate some of the migration methods and allow the organization to zero in on the approaches that are actually possible for them to use.

The decision making process begins by asking whether the on-premises environment runs Exchange Server 2003 or 2007. For those environments the next decision point is whether there are more than 2000 mailboxes. Organizations with fewer than 2000 mailboxes are supported for cutover, staged and hybrid migrations, whereas more than 2000 mailboxes are only supported for staged or hybrid migrations.

The 2000 mailbox limit doesn’t mean that organizations with less than 2000 mailboxes should automatically choose a cutover migration. For example, if the organization wants to migrate their users in smaller batches instead of one big batch then a cutover migration would not be suitable.

When Cutover Migration is either not possible or not desirable for an Exchange Server 2003/2007 organization the remaining options are staged and hybrid migrations. For an Exchange Server 2003 environment a migration to Exchange Server 2010 needs to be completed first. For an Exchange Server 2007 environment at least one Exchange Server 2010 or 2013 server must be installed in the organization to provide the hybrid functionality. Both options require directory synchronization to be implemented. Without directory synchronization, your migration options are limited to third party tools.

To learn more about how to Migrate Email to Office 365 or Office 365 Tenant Migration visit O365CloudExperts.