Hybrid Exchange configuration and deployment checklist

By Steve Goodman,

If you're already running Exchange 2010 or higher, you don't have a plethora of options if you want to migrate mailboxes to Office 365. But that's not necessarily a bad thing; it gives you rich coexistence during the migration, a way back from the cloud if you need one and a greater ability to test.

Think of it as a transition, rather than a migration. Performed correctly, using a hybrid Exchange installation for a migration has the smallest effect on end users when compared to a staged or cutover migration. It also makes use of the skills you already have.

That's not to say a hybrid Exchange environment is always appropriate; small organizations can benefit from the simplicity of a cut-over or staged migration. If you're not running on-premises Exchange, look at products from vendors like MigrationWiz and Quest.

Hybrid challenges for Exchange 2007 and Exchange 2003 organizations

The proper steps to implement a hybrid Exchange environment for Exchange 2003 or 2007 are parallel to an Exchange 2010 migration. People often refer to the "hybrid" server as if it's sitting on the edge of your environment and only used for Office 365. In reality, it's just an Exchange server.

This is where the challenge comes in. You'll need to migrate front-end client access services like AutoDiscover, OWA, EWS or ActiveSync for the hybrid functions. When you're looking at what needs to be done, check out this article on the Exchange Team Blog. You only have one option if you're using Exchange 2003: You need to use Exchange 2010 SP3. If your organization is using Exchange 2007, then you have a few options with Exchange 2010 SP3 or Exchange 2013 CU1.

It's tempting to use the latest version, but you may want to consider Exchange 2010 SP3 first if you're using forms-based authentication within Exchange 2007. This comes down to coexistence; when users login with Exchange 2010 SP3 acting as the "front" for Outlook Web App, they'll automatically be redirected to Exchange 2007's legacy namespace without being prompted again for a password. With Exchange 2013 CU1, the user will be prompted for the password a second time when they are redirected to Exchange 2007, thus requiring a double login.

Migration challenges for Exchange 2010 organizations

There's often confusion around Exchange 2010 and hybrid migrations. One of the most common questions asked is if you need a hybrid server with Exchange 2010. The answer is no.

All Exchange 2010 SP3 Client Access and Hub Transport servers have the code needed to act as hybrid servers. Unless you're looking to migrate to on-premises Exchange 2013, you don't need Exchange 2013 CU1 for a hybrid Exchange migration. It doesn't offer any additional coexistence features.

One area to consider is whether you have some minimal additional capacity; this requires you to support out-of-hours mailbox moves and federated sharing. Most times, you won't have any because you'll move mailboxes to the cloud and free up resources.

Questions may arise as to whether Exchange 2010 SP3 is stable enough to implement in your organization and where it needs to be. Exchange 2010 SP3 is stable, though there have been reports of issues with PDF and WAV files in unusual circumstances that affect a small number of customers. Microsoft has a fix available. You don't need to implement Exchange across your organization. If Exchange is spread across multiple sites, you'll only need to immediately upgrade your Internet-facing sites to SP3.


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