Update [March 18, 2013]:
Read about the latest tools to optimize email deliverability here: Navigating the Fiefdoms: Email Deliverability
Original Post [Published Oct. 3, 2008]:
What happens when you have preached to people so long to add your email address to their address book so that they are a trusted sender and you now are changing that? Have you gone through this change before? It is wise to alert people prior to this change so that you do not end up in their bulk folder before you make this change.
I am not sure overall from an industry perspective of how many subscribers do take the step to add them to a “safe list” but I would bet that this had some people that had not done so before to take that step now.
Is this something you use in your programs at the opt in? And if so do you have any data that you would share on subscribers using it?