I want to add that my Hotmail users are also not receiving their emails. Everything else seems to be going where the need to as far as I can tell (nobody except Hotmail users have been complaining yet).
I tried with my school account (Live/Outlook-based) and mails were going through, although took about 5 minutes (both ways).
I created a Hotmail account and I can confirm that emails from my x10hosting are not reaching Hotmail users. I can, however, send a message from Hotmail to my x10hosting account.