Notwithstanding the fact that they deactivated my mail account and deleted its contents because I didn't log in for 4 months*, I just sent myself an email with the body text "fucking shit cunt felch santorum wank bollocks arse prick" with no problems.
*And nothing of value was lost, but still - a shitty thing to do, especially as it's a ruse to get you to subscribe to their fancy-pants "plus" account.
Other than Flickr, what's the point of Yahoo! any more?