Exchange 2007 conversions start officially on Sept 8. Migration of all mailboxes is likely to take six weeks, and the order in which they are done is pretty random. Each mailbox takes about 30-45 minutes depending on size and once notified, users should be off of Exchange during the migration. 1 GB quotas go into effect with the migration.

Additional disk space can be purchased at a cost of $55.30 / GB / year.