interesting htc said that. i had yahoo working just great on the evo and thus far yahoo has been working well on the 3D.
i know yahoo sent out an email a few weeks ago saying i needed to update to yahoo plus or some such so maybe once this is in place at yahoo perhaps the accounts will stop working in the native app.
i dont use yahoo hardly and installing the yahoo mail app is a resource and battery hog so its not worth to for me to install that.. ill just use my xoom to access yahoo or just use the web based yahoo.
i also agree it may be how one's email settings are set up online...