A hybrid mail interface sets up your mailbox on both on-premise and Exchange online. This setup is either permanent or temporary and it depends on your willingness to fully migrate to Exchange Online/O365.
A hybrid migration allows you to move your entire mailbox to Office 365. Upon migration, you don't need to manually reconfigure and redownload the outlook data. It is configured automatically.
Like an on-prem mailbox, a hybrid solution can 'seed' the cloud mailboxes in the background while Outlook functions as usual. Once you are ready for migration, you can just sync the mailboxes to the new destination.
The challenge of a Hybrid migration.
Hybrid migration sets up your Office landscape for co-existence. Now two servers, the old internal server and the Office 365 handle the emails at the same time. This unnecessarily adds to complexities and takes more system space. This is the reason, organizations seldom get this setup right.
Benefits of a Full Hybrid migration
Co-existence has its benefits too. Now admins can analyze and fix the bugs (if any) and in case of full migration, they can fix these bugs before the organization completely moves to the new system.
This also allows for new configurations to be tested on the Office 365 platform while the old systems such as eDiscovery, archiving and security systems function as usual.
Requirements of a Hybrid migration
a. The On-premise exchange must be 2010, 2013 or 2016 version.
b. The exchange versions (as listed above) must be fully updated and patched.
c. These exchange versions must be running at least one of each type of server role. These server roles include client and mailbox access for 2016, client and mailbox access for 2013, hub transport and client access to 2010).
d. The older exchange versions require third party tools to migrate to Office 365.
e. In order to migrate third party extensions to Cloud, separate migration paths need to be setup. These third-party extensions may include archiving tools, e-discovery, mobile management tools, video conferencing etc.
The Hybrid agent
The most difficult aspect of Hybrid configuration is to publish the Exchange server in such a way that it integrates easily with Hybrid migrations. With Hybrid agent, the process becomes easy. Now you can just install the agent and Office 365 can automatically migrate mailboxes from on-premise.
A minimal hybrid migration is one of options for hybrid migrations. It is also known as express migration as it offers a quick, simple migration approach for simple instances.
Minimal hybrid migration is recommended for specific use cases as organizations can extract maximum benefits in such use cases. The key use cases are listed below:
1) Organizations that do not require enhanced features.
Companies who are not using advanced exchange features like e-discovery, free/busy sharing or workflows etc. can opt for minimal hybrid configuration.
2) Small or medium sized organizations.
Minimal hybrid approach is well suited for medium or small organizations who have less than 2,000 users. These firms can use minimal migration to achieve effects similar to regular migration but with less insurance. It also gives the admins an ability to perform troubleshooting and add configurations before migrating to permanent configurations.
3) Merger or acquisition scenarios
In merger or acquisition scenarios, organizations might benefit from Minimal Hybrid configuration. The configuration gives the organization an option to move the mailboxes to a tenant without having to configure all Hybrid features.
Benefits of Minimal Hybrid configuration
Minimal Hybrid configuration gives you an option to take a test ride with minimal complexities and risks before going for full hybrid implementation.
Minimal Hybrid is focused on full migration and doesn’t encourage long term coexistence of cloud and on-premise configurations. This approach speeds up your full migration strategies.
Features excluded from Minimal Hybrid configuration
1) Cross premises Free/Busy sharing.
2) Outlook Web application (OWA)
3) Outlook Anywhere
5) Archive mailbox automatic retention
Reasons to Choose
1) Full Hybrid Solution
a. You need to leverage both on-prem and cloud mailboxes.
b. You require Full access permissions across exchange and Office 365 mailboxes.
c. You require Teams and Skype for Business integration into Exchange 2016 mailboxes.
d. You require eDiscovery functionality.
1) Minimal Hybrid Solution
a. You require quick migration to O365 and have fewer than 2000 mailboxes to migrate.
b. Your priority is a "cutover migration" to Office 365.
Making the Choice between Full Hybrid and Minimal Hybrid
Below is an informative table which can help you choose between Full Hybrid and Minimal Hybrid based on different use cases.
Quick migration of mailboxes to cloud
Use Hybrid agent as soon as it’s available
Cutover migration to Office 365
Use Azure AD connect to synchronize Active Directory
Global address list between on-premise and Office 365
Transfer organization configuration like ActiveSync policies to Office 365
Route all mail through the existing Exchange Infrastructure
Ensure that email path between on-premise and cloud users is secure.
Configure advanced sharing across Exchange and Office 365 mailboxes
Use advanced integrations like Teams or Skype for Business into Exchange 2016 mailboxes.
Minimal Hybrid approach is built for speed whereas Full Hybrid approach is built for coexistence. As a user, you can decide on the best configuration based on the use cases and your overall strategy in terms of complete cloud adoption. From a Microsoft standpoint, Minimal Hybrid with Hybrid agent is widely promoted to make full migrations much easier.
However Microsoft Team has more functionality in its search box and has an extra vertical panel on far left which has tabs like Activity, Chat, Meetings, Files and Teams.