Email Migration from On-Premises to Cloud

Question

Hello All,

I want to do email migration from On-Premises Exchange server 2013 hosted on windows server 2012 R2 to Exchange Online.

I have approx 10 domains On-Premises where 1 domain e.g. "engineer.com" is logon domain for all the users on-prem and I want it to be migrated to cloud.

For rest of the domains I want them all to be migrated to cloud except 1 "auto.com".

Now the scenario is this like On-Prem as said earlier "engineer.com" is logon domain and and there are several users whose email are also configured with this domain . Other Scenarios -

1. Where "engineer.com" is Primary SMTP and no alias configured. (Should be migrated to cloud)
2. Where "engineer.com" is Primary SMTP and 2-3 other aliases are configured e.g. "robot.com". (Should be migrated to cloud)
3. Where "engineer.com" is Primary SMTP and 2-3 other aliases are amongst which 1 is "auto.com". (Auto.com should stay on-prem).
4. Where "robot.com" is Primary SMTP or any other domain is Primary SMTP and "engineer.com" is alias. (Should be migrated to cloud)
5. Where "auto.com" is Primary SMTP and no alias configured. (Should stay on-prem)
6. Where "auto.com" is Primary SMTP and "engineer.com" or any other domain (which is to be migrated to cloud) is configured as alias.

How to do migration in such scenario? Could anyone please give me step by step procedure on how to do it?

Is Hybrid AD required? My on-prem AD is also WS 2012 R2

Is Hybrid Exchange required?

Answer 1

Hi, @Harsh Jasapara

Migrating an on-premises Exchange to Exchange Online can be complex, especially with the specific requirements of multiple domains and which domains and users need to be migrated. This process often requires a hybrid AD setup to achieve seamless user and mailbox management. You can follow the steps below:1.Prepare the on-premises environment. Ensure your Exchange Server 2013 is up to date. Check and record all domain details and user configurations.

2.Directory synchronisation. Set up Azure AD Connect on an on-premises server to synchronise user and email attributes with Azure AD. This provides a unified identity for users in both on-premises and cloud environments. Ensure to verify the "engineer.com" and other necessary domains in O365.

3.Use the HCW to establish a hybrid connection between Exchange on-premises and Exchange Online. Select the appropriate migration method. More information can be found Decide on a migration path in Exchange Online | Microsoft Learn

4.Create a migration batch for mailboxes based on your specific scenario. Simple migration is recommended for users who have "engineer.com" as their unique or primary SMTP address. Identify users with "auto.com" and separate them. If aliases are involved, those accounts should be excluded from the migration or handled exclusively.

5.Initiate the migration in EAC or PowerShell for the user. Update the MX records and necessary DNS records when you're done.

6.After the user data is successfully migrated and verified, deactivate the on-premises Exchange server as required.

Considering that you have multiple domains and the complexity of your specific needs, it is recommended that you contact phone technical support for more detailed guidance. Find Microsoft 365 for business support phone numbers by country or region - Microsoft 365 admin | Microsoft Learn

Here are some reference articles. Step-by-Step Guide for Exchange 2013 to Office 365 Hybrid Migration - Collaboration - Spiceworks Community

Please Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information. 

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