How could I activate an "autosave" option while writing a message (like in Microsoft word for example)?

I can manually save a message (CTRL + S) while writing, but I don't see how to enable an autosave feature which could be very useful...

When I manually click on CTRL + S, a draft of the message is automatically generated on the outbox folder. I would like to do that automatically each X minutes for exemple.

Because of a crash, I just lost a very long mail I was writing...    ThanKs