This is what HTC sent me today...
I understand that you need to set up your Yahoo email on your we've. From what we've seen, this issue spreads to all Android phones but not necessarily all Yahoo accounts. Yahoo has again restructured their mail setup just enough to make things trickier; at first they had it set up so that you couldn't set it up unless you had their paid Yahoo Plus account. However, a way around that was found. With this latest change that they've made, we've so far found that the best (and possibly only) way to set up a Yahoo account on your device is to download the Yahoo Mail for Android application from the Android Market and set it up that way. That still works even when other methods don't. I do apologize for any inconvenience you may have experienced.
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Edit: And his response after my thanks...
I agree, a long term solution would be much better, and I believe we're looking into that. From what we've gathered it seems like Yahoo is making it so that you HAVE to use the app, which doesn't really make a lot of sense. I'm sure we'll find out more as the issue is investigated, and hopefully that will help us find a long term solution.
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