As they say, if you don’t know your destination, any path can take you there. I can apply this metaphor to Exchange Online Migration planning. For migrations from an existing on-premises exchange server environment, you can migrate all email, calendar items, tasks and contacts from user mailboxes to Office 365. The available methods are cutoverstaged, and Exchange Hybrid migrations. It takes extreme caution and planning to determine which method works best in your case. These migration methods copy over all mail data, including contacts, calendar items, and tasks.

You can also use the Internet Message Access Protocol (IMAP) migration from Exchange servers, and if your Exchange server is older than Exchange 2003, IMAP migration is your only option. Note that IMAP migration will copy over only email data. And then you have migration tools that may ease out your migration efforts at a cost.

To understand this better, it is important to look at business goals for migrating to exchange. The goals can be any of the following or totally different but once identified, they could ease out your decision making in migration approach.

  1. Date driven goal due to hardware constraint or capacity planning.
  2. The total number of users required being migrated.
  3. Current version of exchange server

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. However, mailbox count is not the only parameter to choose migration strategy because, given the circumstances, mailbox count greater than 300 may qualify for hybrid migration instead of a staged or cutover migration.

  1. Cutover migration – When the organization has less than 2000 mailboxes but want to migrate in batches, cut over migration may *not* be the right approach.
  2. Staged migration – You can’t use a staged migration to migrate Exchange 2010 or Exchange 2013 mailboxes to Exchange Online. So unless you use Exchange 2007, Staged Migration would *not* be the right approach.
  3. Hybrid migration – Hybrid migrations require some additional configuration and hardware but they allow the on-premises Exchange organization and Office 365 to function as though they are the same environment with seamless mail flow, a shared address book, and calendar free/busy federation.
  4. Third Party migration tools – Finally, businesses using non-Exchange email platforms can’t use the cutover, staged or hybrid options. For those businesses Microsoft provides an IMAP migration option for moving mailboxes to Office 365, or alternatively, a third party migration tool can be used.

Certainly, there is more to migration strategy than just a straightforward migration approach. Before you embark on your exchange migration journey, engage with an expert.