Migrating off a legacy hosting platform typically involves moving off IMAP.

Below are some general steps that can be followed. Migrating IMAP data from the server can result in gaps, with no calendar or contact data. And some missing inbox data – due to IMAP filtering. Best to do a local export/import using PST data as well.

Microsoft free IMAP tools is available: https://learn.microsoft.com/en-us/exchange/mailbox-migration/migrating-imap-mailboxes/migrating-imap-mailboxes

Or a 3rd Party Tools like migrationwiz can also be used.

A phased migration can be achieved using a complex forwarding setup – ask us for details on how we can provide coexistence for your IMAP migration to 365, as well as a phased migration approach.

General Steps

1. Assess your current environment: Understand the size and complexity of your IMAP hosted mailbox environment. Determine the number of mailboxes, total data size, and any specific requirements or limitations.
2. Set up Office 365: Create an Office 365 subscription and set up the necessary accounts and licenses for your organization. Familiarize yourself with the administration portal and its features.
3. Plan the migration strategy: Decide on the migration approach based on your requirements and available tools. Office 365 provides different migration options, such as cutover migration, staged migration, and hybrid migration. Choose the method that suits your needs best.
4. Verify domain ownership: Verify that you own the domain used for the IMAP mailboxes. This step ensures you have the necessary permissions to migrate the email domain to Office 365.
5. Prepare the source environment: Make sure your IMAP mailboxes are in good shape before migration. Consider removing unnecessary data, such as old emails or large attachments, to reduce the migration size and time.
6. Inform users: Notify your users about the upcoming migration, including any changes they may experience during the process. Provide clear instructions on how to set up their email accounts in Office 365.
7. Configure Office 365 migration settings: Set up the migration endpoint and configure the migration settings within the Office 365 administration portal. Provide the necessary credentials and connection details for the IMAP server.
8. Perform a pilot migration: Select a small group of mailboxes or a test mailbox to perform a pilot migration. This allows you to verify the migration process and address any potential issues before migrating all mailboxes.
9. Start the full migration: Once you have successfully completed the pilot migration, proceed with migrating all the remaining mailboxes. Monitor the progress and ensure that all mailboxes are migrated correctly.
10. Complete the migration: After the migration is complete, perform a final check to ensure all data has been transferred accurately. Test email functionality, calendar synchronization, and any additional features your organization relies on.
11. Update DNS records: Modify your DNS records to point the email traffic to Office 365. Update the MX records, Autodiscover records, and any other relevant DNS settings to ensure emails are delivered to the correct location.
12. Decommission the old environment: Once you have confirmed that everything is functioning correctly in Office 365, decommission the old IMAP environment. Notify your users and ensure they are fully transitioned to Office 365.