It is possible to do, but a bad idea in most cases. Most applications leak sensitive information when using with (or possibly without) Tor. Less importantly, how necessary is it that Google doesn't know where you logged into your email.
Tor Project has a page about Torifying and instructions on specific applications.
For Mozilla Thunderbird it is recommended to use Torbirdy. Installation instructions can be found here.
For a torrenting take a look at this question.
I also recommend the use of Tails as it is a live Linux OS that routes all traffic through Tor.*
The Amnesic Incognito Live System is a live CD/USB distribution preconfigured so that everything is safely routed through Tor and leaves no trace on the local system.
*All of the applications in it are specifically configured to route through Tor and no non-Tor traffic can escape (or at least in theory.) However, it does drop unexpected/non-tor traffic.