I disagree. I've had Yahoo reject my emails completely silently (didn't arrive in inbox OR 'spam' folder, even though Yahoo's MX said the message was accepted).

I disagree. I've had Yahoo reject my emails completely silently (didn't arrive in inbox OR 'spam' folder, even though Yahoo's MX said the message was accepted). Yahoo was entirely unresponsive about this issue. We didn't have the same problem with any other provider and it was resolved immediately upon switching to a third-party email delivery service. Additionally, Yahoo has a huge amount of abuse and doesn't seem to have an abuse handle either; you have to fill out some form buried deep on their site. On the other hand, I've reported abuse incidents to Hotmail before and have gotten an actual reply from a human (a rarity when submitting abuse reports; most places act on them but don't bother responding).