In Office 365 Setup, One of the most important tasks is to perform mailbox migration between the M365 / Office 365 tenants.

A few months back, Microsoft launched something new and amazing in public preview. Please read the article for more details. Cross-tenant mailbox migration - Microsoft 365 Enterprise | Microsoft Docs

In this series of blogs, we are going to find out the prerequisites for cross-tenant mailbox migration.
Please see the listed high-level points for the whole mailbox migration process.

1. Prerequisites
2. Prepare Target Tenant
3. Tips & Tricks - Target Tenant
4. Prepare Source Tenant
5. Tips & Tricks - Source Tenant
6. Steps for Mailbox Migration.

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Prerequisites.

A) Permissions: connect with Exchange Online, and Azure for various tasks like running PowerShell scripts. Mailbox Migration would require setting up Azure Application, Exchange Online Organization Relationship, and many more tasks. Global Admin permission should be enough to execute all steps.

Launch Azure AD Portal - https://aad.portal.azure.com/ .
Go to Azure Active Directory, and Select All Users and type the name of the person in the search bar.

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Click on the Username and Go to Assigned Roles to see your assigned roles to your profile.

B) Mail-enabled Security Group: This is required for the Source environment, you can create a single or multiple mail-enabled security groups to add a list of mailboxes. These are the mailboxes that you want to migrate from the source to the target environment. The purpose of this mail-enabled security group is to restrict/control which mailboxes would be moved out of the source environment.

Note : Please make sure it's not a nested security group.

C) Key Information: Please gather listed information to get started.

• Note Tenant's ID for source and target tenant, you would need it for the execution of PowerShell scripts.
• ResourceTenantAdminEmail - this is the email address for the source admin account.
• SubscriptionId -  make a note for Target Azure Account's Subscription Id where you want to create a resource group to store the key vault / Certificate.
• ResourceGroup - choose a name for the resource group creation.

This would conclude all the prerequisites.

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Next Blog

In the Next part of the blog, we are going to cover the preparation, tips, and tricks on Target Tenant.

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(Standard Disclaimer: All the Information posted in the blog may be out of date in due time or updated by the relevant sources

Perform your due diligence and verify all the information posted here)