That could change.

Microsoft adopts IronPort anti-spam "whitelist"

"WASHINGTON, May 5 (Reuters) - Microsoft Corp. (MSFT) said on Wednesday it has adopted an e-mail "whitelist" program by IronPort Systems Inc. that will allow legitimate marketers to thread the gauntlet of spam filters protecting its inboxes. Microsoft's Hotmail and MSN e-mail services, which together claim 170 million regular users, will require marketers to put money up front if they wish to ensure their messages aren't mistaken for unwanted spam."

Nice word - "marketers".

/Lars.