Emails are currently not being sent to Microsoft emails such as live.com and hotmail.com. The reason is that Microsoft does not use the correct protocols, regardless of outrage among email postmasters. Instead of using SPF 1.0 like Gmail, Yahoo, and everyone else, Microsoft chooses to use a non-official standard that was never fully passed by the IETF called Sender-ID. The problem with this is that oftentimes in order to satisfy the masses with SPF 1.0, you're breaking compatibility with Sender-ID verification.
Now, I think I found a workaround by putting a blank Sender-ID record on ponycrush.com, so theoretically Microsoft will use the correct standards as a last resort. ( lolwut ) Hopefully it'll work, but we won't know until next Monday.