How do archiving or content retention affect my migration?
MigrationWiz will preserve all dates associated with your email data, except for the creation date, of course. As each item gets created at the Destination, the create date is set to the current time. Other properties such as the received date, the sent date, etc., remain identical to what they were at the Source.
We find that most archiving and content policies do not evaluate the creation date, but do evaluate other dates, such as the received date. Therefore, it is likely that archiving and content policies will process migrated emails. You can learn more about how dates are evaluated here: http://technet.microsoft.com/en-us/library/bb430780.aspx.
If you are migrating to Office 365, note that default archiving policies will move items older than two years to the archive mailbox.