There was a reason I didn't like the Thunderbird mail client, Tony, and that is, the preferences don't appear in the about:config list of Firefox, and I couldn't find a way to access the Thunderbird preferences in the same way. The reason being, I wanted to maintain my beige coloured background to my outgoing mail, which I had to apply to the about:config list in Mozilla, as the default options didn't contain the colour I wanted. Also, I couldn't get Thunderbird to fire up from external 'mailto:' links. Outlook kept appearing instead, but I think I might have a solution to that now.
I would also miss the HTML editor (Composer) in Mozilla, which is really handy for putting stuff up on eBay, so although I am aware that Firefox is an excellent step forward, and has some very nice features, on balance, I think I'll be sticking to good old Moz for now.