is it normal for a guy to say "kisses" after he's writing an email to you?
As a guy.
No it isn't common. Depending - I can't speak for the world - But Generally guys aren't quite so free about syaing things like this.
If I put an "X" after i've types or written something, I meant it - I don't put them down lightly. If i put them down I'm very happy with ya ;)