How long will the import take?
For email migrations, thousands of messages per hour will be transferred, but it is difficult to estimate the total transfer time because there are many factors. The size of the source account has the largest impact on transfer time. In ideal conditions, 250-500 MB will be transferred per hour. Larger accounts take longer to migrate, so if you plan to delete a large number of emails, you can save some migration time by doing so before beginning your migration.
Many contacts imports finish in less than a minute, and most finish in less than five minutes. The number of contacts in your address book has the largest impact on transfer time.