In this article we will be talking in details about the hybrid models that help us to have a hybrid setup of our Exchange Server along Exchange Online as well as a migration method to Exchange Online. We will go through all the details and information to help us in the decision for the migration effort of the organization. We will also be talking about alternative third-party tools that specialize in the matter and how can these be beneficial for the project.
What is Exchange Hybrid?
When having a hybrid deployment with an Exchange Server, this will setup a link between the on-premises Exchange Server and the Exchange Online on Office 365. This will create a unified integration where both Exchange systems act as one and mailboxes or other resources can reside on the local or the cloud, and both systems acting as one Exchange Server creating a deep integration. Features of a hybrid deployment include the following
- Seamless data and mail flow between the on-premise and cloud.
- Unified Global Address List (GAL).
- Sharing of free/busy calendar information.
- A consistent Microsoft Outlook experience to the user.
There is a consistent experience for the user as the hybrid deployment will automatically switch the Outlook profile and the user will not know or will not be impacted if the mailbox is on premises or cloud.
There are two deployment methods for hybrid deployments.
Full Hybrid is best for large organizations which will have long coexistence with the cloud. Large organizations will not have a quick migrating process and this method would be the best solution. This method offers rich calendar sharing features as well as it provides the deepest integration possible.
Minimal Hybrid is ideal for a small organization with minimal migration efforts of mailboxes to the cloud. Although it does support some calendar sharing, it doesn’t support detailed and cross-premises delegation, no centralized mail transport and not supporting long-term coexistence. The minimal hybrid model as it describes itself is the ideal method when you don’t have a complex setup, there is no need for cross-premises delegation and no coexistence. The benefit of it is that it’s simpler to setup without any major effort.
How mail flow works?
When having a hybrid model, in the case of full hybrid, all emails flow through the on-premises server (being cloud of local). This will give you full control over mail routing but there are more complexity and increased load on the on-premise server. There is the thing that if the MX record is pointing to the local Exchange Server, if the server is not available, the online mailboxes will still not receive emails as the mail flow depends on the local server.
One can change the MX record to pass all through the cloud, but some organizations would prefer to keep the mail flow centralized on their local servers for compliance or regulatory restrictions.
Mailbox migration using Hybrid
Since the local Exchange Server and Exchange Online work as one, a mailbox of a user must reside in either the local or cloud Exchange. When it comes to movement of mailboxes from one to the other, below is how it works.
From the admin center, being local or cloud, the administrator will initiate a move request. This move will not impact or limit the user. The mailbox will start seeding to the destination. Once it has done a full seed in the background the mailbox will be available to complete the migration. During this process the Outlook application may reconnect automatically while it automatically connects the profile to the cloud or vice versa. This is totally transparent to the user and the user might be disconnected for a short period during the completion of the mailbox since it will seed the few changes from the full seed.
Constraints and challenges
Although a migration method is more seamless and smoother, one must take in consideration some of the constraints and challengers that one could face.
- There are different components which could result into multiple points of failures like the Entra Connect, the Exchange Server, network, and complexity of the system.
- Dependency on the Active Directory configuration like different domains, matching issues, attribute conflicts and other.
- One must maintain the entire system until decommissioned. This means that all the Exchange Servers must be up to data, Active Directory Serves, Entra Connect server and also one must keep the certificates in check and connectors for proper binding as misconfiguration of certificates or expired certificates will affect the migration and hybrid.
- The Hybrid Configuration Wizard (HCW) assumes that your Active Directory is healthy and it cannot fix the underlying issues or misconfiguration in the Active Directory.
- Complexity when it comes to the setup can lead to coexistence issues like free/busy, calendar delegations, and mail tips issues, while also including Global Address List (GAL) synchronization issues and other user issues.
Using third-party tools
For the migration effort to be as smooth as possible and easy as possible with less complexities, less point of failures, and less configurations, one should look at the alternatives in the market. Specialized tools such as Stellar Migrator for Exchange can help bridge this challenge and offer a cross-forest migration tool with delta (incremental) migrations. The tool also allows the granular migration with filtering options that allow user mailboxes, archives, shared mailboxes, and public folders migrations using the following path.
- Exchange Server to Exchange Server
- Exchange Server to Office 365
- Office 365 to Office 365
- Office 365 to Exchange Server
Other features to complement and facilitate the migration of data include automatic mailbox matching, priority and performance migrations with detailed real-time reporting and post migration reporting.
Conclusion
As we have seen in this article, the hybrid model comes with a number of features and options for a seamless migration to Office 365 as well as a hybrid model if one would need to have both environments running. There are a number of constraints, requirements and other things that could go wrong, not including some of the complexities that one might encounter in the setup, so what one must do is to evaluate the migration method before venturing into is to evaluate other solution which would facilitate the process and guarantee data integrity and flexibility.
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