Office 365 Partner Community: focus on hybrid – Planning considerations for an Exchange hybrid environment

by Mattia Tocco
Lead PSC for Unified Communications
Global Partner Services Delivery

The Office 365 Partner Community is led by National Partner Technology Strategists from the Microsoft US Partner Team. Partner Community activities include blog posts, discussions on Yammer, newsletters, and community calls.

This is part 2 of our Office 365 Partner Community blog series about Office 365 hybrid. Read part 1, and watch our community call presentation online.

Planning considerations for an Exchange hybrid environment

While planning to move a customer’s email system to Exchange Online, there are different areas that impact the specific solution that you could adopt to perform this activity. In this post, I’ll cover the key points to take into account when deciding how to move mailboxes to the cloud, with a focus on the hybrid architecture.

Below are some of the factors that impact the plan for migrating your mailboxes to Exchange Online. For each one of these factors, there are common considerations that lead to plan an Exchange Hybrid solution:



You can implement an Exchange Hybrid architecture only if the on-premises infrastructure is based on one of the following Exchange versions: Exchange 2010 or Exchange 2013. If the source environment is Exchange 2003 or Exchange 2007, it is possible to have a hybrid environment by installing an Exchange 2010 SP3 (if you have Exchange 2003) or an Exchange 2013 (if you have Exchange 2007).

In these scenarios, the Exchange 2010 or Exchange 2013 servers installed will be provided for free. You can request a key to use to install the server that will be used for configuring the hybrid environment here.

Size The ideal customer target for Exchange Hybrid architecture is a medium-large company that doesn’t want to migrate its messaging system completely to the cloud, usually due to internal requirements.
Coexistence Exchange Hybrid provides the richest coexistence between our on-premises and online messaging solutions. This is a key point in determining the adoption of a hybrid solution.
Provisioning As soon as you implement an Exchange Hybrid architecture, you can decide which mailboxes stay on-premises and which are moved to the cloud. A mailbox can be moved back to an on-premises environment if necessary.
Identity management Directory Synchronization is the minimum requirement for a hybrid environment. ADFS is optional and needed only by specific scenarios (e.g., to avoid multiple credentials requests for the users, third-party Multi-Factor Authentication, limit access to Office 365 based on client location, etc.). In some cases, a solution based on directory synchronization with password synchronization could be enough for satisfying the customer’s identity requirements.

How Exchange Hybrid helps create good user experiences

From a user perspective, configuring a hybrid environment makes sense, so that there is no loss of important messaging capabilities. With Exchange Hybrid, users with mailboxes hosted on-premises and users with mailboxes hosted in the cloud will have the same features available to them. If Exchange Hybrid is not configured, and the two environments (on-premises and cloud) are kept separate, here is how users are affected in three key areas: Messaging, Calendaring and Free/Busy, and Address Book.


In separate on-premises and cloud environments, a user hosted on-premises sees a user hosted in the cloud as an external user, and vice versa. In the example below, an on-premises mailbox user sending an email to an online mailbox user gets a message in Outlook that his recipient is an external user.


Using the same scenario as above, this time with hybrid implemented, the user is recognized as an internal user. This is beneficial for all rules that are based on the user’s location.


Calendaring and Free/Busy

For users in the separate environments, calendar and free/busy information is not available.


With Exchange Hybrid configured, the two users can each see the other’s calendar and free/busy information.


Address Book

A user with an on-premises mailbox can’t see the contact information stored on the address book for the user with an online mailbox at the same company if Exchange Hybrid is not configured.


With Exchange Hybrid configured, users can see Address Book information for their co-workers, regardless of where their mailboxes are hosted.


The IT experience with a hybrid environment

  • Administration. A hybrid deployment in Exchange 2013 is administered via a single unified management console that allows for managing both on-premises and Office 365 Exchange Online organizations.
  • Mail routing. In a hybrid scenario mail flow Cloud<->On-premises is secured and messages are treated as Internal by Transport rules and clients.
  • Mailbox move. Move Mailbox operations are performed online by the Mailbox Replication Service and there is no need to re-synchronize the OST file. More information about this topic.

Steps to Exchange Hybrid configuration

Configuring an Exchange Hybrid environment requires activities on both Office 365 and Exchange Server. These are the macro activities that you should perform on each one of the systems. While Exchange 2013 is mentioned in the below graphic, the hybrid environment could also be based on Exchange 2010 (required if the hybrid environment is is for Exchange 2003).


Here are useful links for configuring and troubleshooting a hybrid environment:

This 20-minute video by Partner Technical Services explains the configuration steps needed to set up a hybrid environment. This video is part of our Office 365 Deployment Fast Start playlist that covers mailbox migration strategies.

Ask the Experts online series

This weekly series features a 30-minute presentation that is followed by 30 minutes of Q & A where you have an opportunity to ask questions related to your specific project. Here are upcoming sessions related specifically to hybrid environments:

These upcoming webcasts may also be of interest to you. More Office 365 training offered by Partner Technical Services is posted here, and is always part of the US partner training schedule.

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Office 365 community - April 2 call tile

The next Office 365 Partner Community call is on Thursday, April 2. Register here.





Previous Office 365 Partner Community topics

Focus on FastTrack “Getting Started”

Focus on Identity Integration

Focus on Enterprise Voice for Office 365 customers

Focus on Security and Compliance

Focus on OneDrive for Business

Focus on Office 365 Hybrid

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