In a mutual relationship, it is best to break up face-to-face, or, if long-distance, on the phone. The exception to this is if the relationship was in any way abusive and you are afraid for your safety. In this case, break up in any way that will get you (and your possessions, if you lived together) out, SAFE. In your case, I would say that by phone is the best. If you absolutely cannot get the words out by phone, it may actually be kinder to email, so you can take the time to say what you want in a kind way, and then offer the person the opportunity to call you at any time to discuss things. This makes you open to communication, but makes sure you say what you really mean instead of clamming up. It also allows the other person time to digest their feelings in private, before talking to you. Still, if you can manage, most people would agree that breaking up via some sort of mutual conversation is better than reading a one-sided letter. I don't think it would be right for your partner to travel many miles to see you just to be broken up with. Good luck.