Crack a specific email account?

Is it possible to crack an Specific E-mail account?

If it is possible, is there anyone who could tell me how it works?

I don't think so. These leaks are coming from somewhere. Do you really think someone would hack in just to leak one specific mail? A chance that your target's pass leaks by itself is like playing lotto.
There's always a bruteforce method, but it's impractically slow. Oh, and also you can kind of guess one's security questions by social engineering. This is the fun and relatively easy stuff :D
That's what I'm aware of and take it with a grain of salt as I'm not an expert by any means.