mhm... maybe i'm missing your point here completely, but: i simply select them all and then delete them by tapping on the bin. the only thing that doesnt work for me is selecting multiple mails when they're not listed together - like what you'd do with ctrl+click in windows. but as long as they're grouped together, no problem. (which, of course, is not meant to say the built-in client can effectively handle large volumes of email. maybe for the average home user it doesnt have to.)