Yahoo Mail isn't working?

[Lady Nimue]

I can't seem to get any emails sent from personal email addresses. Notifications from Facebook, Twitter, etc., come through fine (as do group messages), but emails sent directly to me from an independent email account don't seem to be coming through. A friend sent me the same email three times over the course of two days, and I have yet to receive a single one of them. What's going on?

(Before anyone asks, I've checked my Bulk mail folder, they're not in there.)