How to migrate your Exchange server to Office 365

geese birds migration sky

It's easy to decide to use Office 365 for email, but not so easy to actually move from on-premises Exchange

Office 365 has been touted as Microsoft's fastest growing business ever. Still, some organizations are stalling when it comes to moving mailboxes from on-premises Exchange to Office 365's cloud Exchange. What's the holdup?

For some, the need to plan and execute the transition may be competing with other day-to-day issues, delaying the Office 365 Exchange migration. Some may have jumped in and purchased licenses without considering some of the migration gotchas (such as mailbox moves and legacy archive issues).

First steps to getting your migration going

Sometimes a little help can go a long way to getting you to actually make the move to Office 365. Knowing this, Microsoft has released the Office 365 Deployment Center, but note that one of its adoption programs expires on March 31, 2015, so now's a good time to review Microsoft's offerings.

If you have an Office 365 portal, look into the Exchange Admin Center for your organization and explore the Migration tab (under the Recipients feature). Options include:

  • Remote move migration (supported by Exchange Server 2010 and later versions). This requires a hybrid configuration between your on-premises Exchange and Office 365.
  • Staged migration (supported only by Exchange Server 2003 and 2007).
  • Cutover migration (supported by Exchange Server 2003 and later versions). Use of this option is permitted only if you have fewer than 2,000 mailboxes. If you have more than 2,000 mailboxes, you must use either staged migration (on Exchange 2003 and 2007) or remote migration (on Exchange 2010 and 2013).
  • IMAP migration (supported by both Exchange and other email systems) for those of you folks looking to migrate from Google and so on.

The hybrid deployment option provides a variety of features, including:

  • a shared domain space (such as
  • a unified global address list (GAL)
  • free/busy calendar sharing
  • onboarding and offboarding at will between the two platforms (note that bandwidth and throttling affect the speed of these processes)
  • centralized mailbox management through a single console (the Exchange Admin Center from on-premises Exchange 2013).

What you need to know for a hybrid migration

If you're performing a hybrid configuration with a remote move migration, you'll find it takes a little bit of time and research to get everything up and running smoothly.

In some cases, it might be worth hiring Microsoft's FastTrack team or a third-party professional services team, as they will have seen all the snafus that come with migration and know how to prevent and deal with them.

If you are a bit more adventurous, you'll want to read up on the migration process, which starts with dropping in an Exchange 2013 system into your environment to run the Hybrid Configuration wizard. (You can make a hybrid connection with Exchange 2010 SP3, but Microsoft documents the process with the 2013 server, which has the wizard built in.)

The hybrid process has a variety of prerequisites, including Active Directory synchronization through the Azure Active Directory Sync tool. This prerequisite helps keep your on-premises Active Directory and your Office 365 directory in sync.

And although it's not a requirement for hybrid deployments, you might want to setup single sign-on so that users can access on-premises and online features with the same username and password.

Note: Both the Active Directory sync and SSO services should be deployed before running the hybrid configuration wizard.

Microsoft provides some helpful tools for hybrid migration, including the Deployment Assistant, a fantastic tool for obtaining step-by-step instruction for greenfield deployments, coexistence deployments, and migration-focused deployments. Another great Microsoft tool is the Remote Connectivity Analyzer, a free online tool that lets you test your connectivity and see where adjustments may need to be made.

The point is, don't remain in Office 365 limbo. If you've decided to migrate to Office 365 for Exchange, make it happen.

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