FYI-I just updated my profile and prl 15 min ago and now my Yahoo mail is working with the native HTC email app!! Not sure if updating those two things fixed it or not. Mine hadn't worked since 6/23. Maybe worth trying??
I couldn't get PRL or Profile to download while using Launcher Pro, but after a reboot, phone "decided" to default back to Sense and both PRL and Profile Update worked. Receiving mail again and can see Folders.
I also updated my PRL and Profile, re added my yahoo account to the HTC mail app and all my emails plus a couple new ones have come in!!!! I also verified that it is auto syncing.