Make a list of shared mailboxes as you will need to add them again after migration
Recurring meetings will not be migrated as you can’t change them afterwards. You will have to delete the meetings before the migration and send a new invitation after the migration. Be sure to make an overview.
List your existing Outlook rules (make a screenshot) as you will need to add them again after migration
Clean up your Mailbox. Empty deleted items folder in Outlook.
External guests on your Teams and Sharepoint Online sites cannot be migrated. Make a list of who still needs access after the migration. Take into account that SD Worx colleagues will not be external guests anymore.
Also list the external Teams sites you are member of (customers, suppliers, …). You will have to be re-invited with your @sdworx.com account after migration.
Clean up your OneDrive and remove all obsolete items. Also make sure it’s completely synced.