Best way to add new email address domain for Hybrid

Question

Hiya

We are hybrid, so all mailboxes live in the cloud and only use the Exchange Server 2019 management boxes to relay email from apps and create users (shared mailboxes, distributions lists)

I need to add a new email domain for all (users, smb and dls) and set it as Default and keep the old email domain.

The current default domain is: contoso.co.us and new one is contoso.us

I understand that I need to go thru these tasks:

1. Create an accepted domain as contoso.us on-prem and online and set both as Authoritative
2. Edit on-prem email address policies, modify the current one and add the new domain (alias@contoso.uk)
   1. I think this will only apply to new accounts.
3. PowerShell script on-prem side to modify all mailboxes to SMTP: alias@contoso.us and make the current smtp: alias@contoso.co.us
   1. Can you recommend a good script please?
4. Anything else to complete?

Thanks

Answer 1

3. PowerShell script

Please understand PowerShell script is not supported in Microsoft Q&A, but you could refer to the following articles: Bulk add secondary SMTP address with PowerShell - ALI TAJRAN

4.Anything else to complete? You also need to makes this new domain name could be chosen as UPN when creating mailbox/AD: Add this new domain name as alterative UPN suffixes from Active Directory Domain and Trusts. Then you will could change UPN for those old mailboxes.

 

Add a new domain to an existing Hybrid Exchange configuration | Peter Klapwijk - In The Cloud 24-7 (inthecloud247.com)

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