If you're curious as to why the Add2Exchange setup process involves changing throttling policies for the Add2Exchange service account on Exchange 2007 and up, here's a good article from the How Exchange Works blog:
http://howexchangeworks.com/2011/11/why-do-we-need-new-throttling-policy.html?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+howexchangeworks+%28How+Exchange+Works%29