No C for me please...
From /.: Too Cool For Secure Code
In no small part, it's because programmers aren't using appropriate tools. In an age where processing power is cheap, there's no excuse for a mail client written in C or C++. For users accessing mail via IMAP or POP, network speed and congestion have a greater influence over performance than anything done on the client side; even for users with local mailboxes, I doubt that we're looking at a huge performance hit.
I had to do some C coding for a job lately. Ever time I wander into C I'm absolutely terrified I'm going to make a stupid error and end up with a buffer overflow bug. I was a lot more confident this time 'round, but still... make mine python.