It is impossible to ignore the basic details of the target and source systems in a migration project. Both systems will likely need to be re-set after migration. Source system configuration problems:- Mail migrations that don't have the correct information from the source system will fail. Common problems include using email aliases rather than SMTP addresses. This makes it difficult for the mail migration tool identify the originating mailboxes. Another problem is that the admin password expires in the middle of a migration. Some mail migration tools use one account that has impersonation rights for all user accounts. These rights must be granted at source (or through self-service tools available to end-users who want to initiate their own migrations). Incomplete setup of the target system: Mailboxes cannot be moved to a target system until it is ready to receive the data. Before migration, the target system must have sufficient licenses to support all users. The target system must also provision the users, as otherwise mail cannot be copied to the inboxes. Post-migration surprises:- Your mailbox migration might require an update to your global address book or tweaks to user terminals, if mail is being accessed via a client. Mail migration may also require domain name moves. These processes should be completed before, during, and after the migration. These are just a few of the tasks you need to address in order for a successful migration.