Hotmail's antispam measures snuff out legit emails too

[OrangeCrate]

Hotmail users and email server admins, beware: you may be unknowingly caught in the crossfire of Microsoft's war on spam. Unintended casualties include legitimate emails from domains with well-established reputations, which are systematically blocked with absolutely no notice and little recourse...

http://www.theregister.co.uk/2007/05/01/hotmail_friendly_fire/