Version: (using KDE Devel) Installed from: Compiled sources I tested to see what KMail would do with "From: one-person@bla, another-person@bla" since I noticed the RFCs allowed it... The Reply button only sets the To address to the latter of the two From addresses, when it should probably: If there is a Sender header (which there was, in this case), use that address for the reply If not, act like Reply to Author (which sends to both)
Kmail from KDE 4.3 sets all From addresses into multiple To headers.