PST import - archived by date imported or date email received

Hi there, 

If I import an old pst file into an Exchange 2010 mailbox, which is going to be archived by EV10, will it use the date the email was originally received, or the date from import?

secondly, if I have a policy that deletes emails over 24 months old, will these be deleted immediately or will EV use the date from import?

Thanks guys