@27631 It's a matter of performance. When you create an email archive, you're moving a lot of the email content off email servers and onto archive servers. If that's already in place, when you migrate (e.g., from Microsoft Exchange 2000 to 2003) you generally have a lot less content on the email server that you need to migrate. This makes the migration process faster and less disruptive.
Listen to the Email archiving FAQ audiocast here.
Go back to the beginning of the Email Archiving FAQ Guide.