Recently we reviewed some of the key insights your IT Team should be thinking about before jumping into Office 365.  You can get the scoop on this thought process here.  It’s important understand the foundations before leaping into your next big decision for Office 365, and that involves understanding the technical considerations for deploying with an Office 365 Hybrid approach.  Office 365 Hybrid for many organizations is the most seamless migration approach if this becomes your preferred deployment approach.

So, let’s dive in and lay out the technical facts about the hybrid concepts and changes that you should understand before moving forward with your implementation.

Office 365 Hybrid Directory Synchronization

In an Office 365 Hybrid model directory synchronization is a very important process.  It ensures that your environment on-premises, and your Office 365 tenant can coexist from a user account perspective.   Directory synchronization ensures that your organizational users have a common view of address books regardless of whether the user account in on-premises or in the cloud.  Now with the option to provision your accounts in either location.  Directory Synchronization is key to ensuring your accounts are in sync between your two environments.

Microsoft has created multiple tools to handle your active directory synchronization between, but the one that you should be using for any deployment at this time due to support changes is Azure AD Connect.

Be Prepared to Reconfigure Autodiscover

Whether you have Exchange on-premises or an Exchange Online configuration in Office 365, autodiscover is used to ensure that the Outlook Client can locate the mailbox even after being moved.  This is part of why when you move a mailbox around between Exchange servers, and even Exchange databases Outlook knows where to find your email data.

How is this configured?  Get ready to configure this in DNS, be sure that the following records are in place and you will be all set.

  • On-premises:
  • Exchange Online:

Exchange On-premises Versions

Keep in mind that to properly configuration Office 365 Hybrid the following Exchange On-premises versions have certain requirements as shown below.

  • Exchange 2010 – Requires an Exchange 2010, 2013, or 2016 Hybrid Configuration
  • Exchange 2013 – Requires an Exchange 2013, or 2016 Hybrid Configuration
  • Exchange 2016 – Requires an Exchange 2016 Hybrid Configuration

Also, important to note that Hybrid deployments always require the latest cumulative update or rollup in your on-premises organization!!

Securing your Mail Flow

If you have internal users on-premises and internal users in the cloud well, then their email will likely transfer through the internet even for an internal email delivery at some point.  Also, keep in mind that your send connector will contain the host name for on-premises organization.  This means that your mail will be treated differently bypassing Anti-spam filters.  So, to ensure the integrity and safety of your corporate messages email should be setup to use TLS with a 3rd party certificate.  Then ensures that your corporate email messages will be fully encrypted during transit.  Given all the security breaches and data leaks that meet the press these days this step is crucial to your deployment.

Office 365 Architecture

When you are deploying Office 365 Hybrid the architecture for your environment will change.  The following diagram from Microsoft highlights the core components that you should become familiar with in advance of any deployment.  Internalize this conceptually and then apply to your existing Exchange deployment.

Office 365 Architecture

Hybrid Deployment

Implementing Office 365 doesn’t come without planning.  Planning is crucial to the success of this implementation type, but in the way of approaches to migrate to Office 365 this is in my opinion the way to go.  Not only will you get the best user experience, you will now have failback capabilities just in case that should ever become necessary.  Cheers!