One of the more attractive options for getting a company to Exchange Online is to use the hybrid deployment approach described in Exchange Server hybrid deployments. This is the only option that allows you to easily on-board and off-board mailboxes (all other native options are on-board only). In addition to the ability to off-board, a hybrid configuration has the following key options.
This topic will help you understand the options for decommissioning Exchange hybrid, and when each of those options should be implemented. There are many variances in when and how to decommission Exchange hybrid servers. Taking the time to understand the implications and properly plan the full or partial decommissioning of on-premises servers is important.
- Cross-premises availability. This allows you to see a user’s free/busy information while scheduling a meeting, regardless of their mailbox premises.
- Cross-premises archive. This allows a customer to move only a user’s archive mailbox to the cloud. This is often the first step for customers to try Office 365, and, more specifically, Exchange Online.
- Cross-premises discovery searches. This allows a customer to perform an e-discovery search that will crawl mailboxes and archives in both premises (this requires you to configure OAuth authentication).
- Outlook Web App URL redirection. This allows for users to be redirected to the proper premises for Outlook Web App access.
- No profile recreation after move. Unlike other migration options, the mailbox GUID doesn’t change. This means that you do not have to recreate your profile or re-download the OST after a mailbox move.
Depending on your organization’s needs, a hybrid deployment is the best option for providing the most seamless user and coexistence experience.
Read more on Microsoft Docs