Typically only mail that is new from the activation time is pushed to the device. BIS pushes emails to your BB items that are new...it does not grab the email history.
There must be some setting in your exchange environment or on the PC's email client such a forward or a rule of some sort that is causing it to happen. That would be where I would start looking anyway.
Last edited by Dubdub : 08-28-2009 at 05:12 PM.