Apple Acknowledges Continuing Issues With OS X Mail, Offers Manual Workaround ⇥ macrumors.com
I reported this as a bug in the third beta of Mavericks and it was closed as a duplicate. I’m surprised it wasn’t fixed by the time the OS shipped, nor in 10.9.1. I hope this gets fixed in 10.9.2 because this workaround is idiotic.