Any WordPress experts out there?

Anyone reading this know much about how WordPress works? I have a big problem with it. Suddenly all email from it stopped working. I don’t get any notifications of any sort, not for comments, recovering lost passwords, the people who subscribe to updates don’t get mail and same for subscribe to comments. The entire email system for it just up and died for no reason. I didn’t install anything new and nothing changed on the hosts end. I am pulling out my hair trying to figure out why it just quit on me, not to mention that was a huge function that myself and many people relied on. If anyone has any ideas on how to fix it, PLEASE let me know.

UPDATE: I seem to have gotten it to work to where I get email notifications for comments, but only the comments from posts created using WordPress, older comments from when I used MT don’t send me emails, but that is how it worked when I installed this thing in the first place for whatever reason. My email system for subsribers is still broken however.