how to import an external exchange mailbox to M365

Question

how to import an external exchange mailbox to M365

Answer 1

Hi Jeroen Koninkx,

Welcome to Microsoft Q&A Forum! 

Have a good day and I hope you're doing well! 

Based on my research, I understand that moving email data to a new environment is an important task, and I would be happy to assist you with this process. 

To narrow down the issue and provide the best advice, could you please clarify how many mailboxes you need to import from the external Exchange to Microsoft 365? 

1. If the number of mailboxes is low (Individual use): You don't need to perform a complex migration. Instead, you could try to import .pst files after having a mailbox set up on the M365 side. 

• Export your current mailbox data to a .pst file via the Outlook desktop app. 
• Configure your new M365 account in Outlook. 
• Use the Import/Export wizard to import the .pst file into your M365 account. 

Reference Article: Import email, contacts, and calendar from an Outlook .pst file 

2. If you have many mailboxes (Admin/Organization level): If you are migrating many users, manual PST import via Outlook would not be efficient. In this case, you can consider: 

• Using the Migration tools in the Exchange Admin Center 
• Or using the Network Upload service to import multiple PST files in bulk directly to Microsoft 365 

Reference Articles: 

• Ways to migrate multiple email accounts to Microsoft 365 
• Use network upload to import your organization's PST files 

Hope this information is helpful, at least partially. If you have any concerns or questions, or if I misunderstood or was unclear about anything, feel free to let me know. 

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Answer 2

To import an external Exchange mailbox to Microsoft 365 (M365), you can follow these general steps:

1. Determine the Migration Method: Depending on your current setup, you can choose between different migration methods such as cutover migration, staged migration, or IMAP migration. The cutover migration is suitable for migrating fewer than 2,000 mailboxes at once, while IMAP migration is for non-Exchange mail systems.
2. Prepare Your Environment: Ensure that your M365 environment is ready for the migration. This includes setting up the necessary permissions and ensuring that your users are prepared for the transition.
3. Use the Exchange Admin Center: Sign in to the Microsoft 365 portal, navigate to the Exchange Admin Center, and create a migration batch. You will need to provide a list of users to migrate, typically using a CSV file.
4. Monitor the Migration: After starting the migration batch, monitor the progress through the Exchange Admin Center. You can check for any errors and ensure that all mailboxes are migrated successfully.
5. Post-Migration Tasks: Once the migration is complete, you may need to update DNS records, inform users about their new mailboxes, and perform any necessary cleanup tasks.

For detailed instructions on each step, you can refer to the Microsoft documentation on mailbox migration.

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References:

• Ways to migrate multiple email accounts to Microsoft 365 or Office 365
• How to migrate mailbox data by using the Exchange Admin Center in Microsoft 365