Nothing will get you rejected faster than hiding/lying. Don't email them ahead of time because that gives them time to formulate their own weird conceptions about what stuttering is or isn't. Be prepared to bring it up immediately, right after you introduce yourself with "hi my name is____". I say something along the lines of " you probably noticed I have a stutter, it's not just a nervous thing, it comes and goes. I'm aware of it and it's something I'm always working on and I'm happy to answer any questions you may have about it. It doesn't prevent me from participating in class, interacting with others and doing what needs to be done " (hopefully that's true) That 60 second blurb after you introduce yourself is all you need to say, it shows you're not trying to hide anything and you own it. After that just get on with showing them who you are beyond that. Good luck!