You make a fine point but the person you are responding does contribute to the effort. I personnally disliked Thunderbird as I found the UI to be quite clunky

You make a fine point but the person you are responding does contribute to the effort. I personnally disliked Thunderbird as I found the UI to be quite clunky but it seems that it's headed in a good direction since a few years and it's already looking much better now. On the other hand something that should be as easy as finding a email... do I have to search into each account ? Not great. Maybe there's a way but if it's not obvious to me the computer guy, it's not going to be obvious to the casual user.