Don't know where the right place is to post this, but I have just solved a problem that was really bugging me with the mail and want to share it - its probably obvious to many people, but the 'send to my email' function wasn't working because I had
myusername@gmail.com authorised on the amazon kindle preferences as @gmail.com, when it is in fact @googlemail.com. This is odd because if i email myself @gmail.com i receive the mail, but I guess for amazon's purposes it doesn't recognise this. Calibre said everything was working okay, but obviously it cant know whether the kindle received my mail or not. Anyway, thanks for calibre!