You know your long distance relationship isn't working and it's time to cut ties, but you can't break up with him face-to-face like you've been able to do with your previous boyfriends. That doesn't mean you're a horrible person for having to do it without him being in front of you. You could be waiting months before you actually have a chance to do it in person. It's not going to be an easy situation, but feeling stuck in a relationship you no longer want to be in is no way to live your life. A long distance relationship has a different set of rules and courtesies than a regular relationship.
The worst thing to do is to break up with your long distance boyfriend over text message, email or some other form of electronic communication. Not only is it impersonal, but it also leaves him with a constant physical reminder of the breakup. Call him when he has time to talk, but also when you know he's not going off to work or has another important obligation. It puts him in a position to possibly have no choice but to deal with his emotions in front of other people.
Make the Call Short
A prolonged phone call can only make the situation worse. If you chat for awhile before you break up with him, the break up can completely catch him off guard even more than if you were to do it from the start of the call. For example, avoid saying "Oh my day was great. I got a raise and went out to dinner. By the way..." After you briefly tell him how you feel, tell him you will send his things the following day and that you think it's best you not talk for awhile, then say goodbye. At that point, it's highly unlikely anything you say will make the situation easier, so it's better to give both of you a chance to process the information and calm the emotions instead of proceeding with the conversation.
Send His Things
If his family happens to live near you, it could be a very uncomfortable situation for you to drop his things off at their house. Get his address before you break up with him otherwise he may refuse to give it to you after in hopes that he'll have an excuse to see you in person. Don't dump his items in the box or shred them to bits -send everything intact and packaged properly even if you are furious with him for a specific reason. Make sure to also get a delivery confirmation slip when you mail the package so he can't say you never mailed it or he never got it.
Don't Talk For Awhile
After you hang up with him, he may try to contact you - don't respond to him. If you already told him that you don't think it's best to talk at that point in time, he knows where you stand. Follow through and he'll know you mean what you said. Give him time, otherwise, both of you may say things that you'll regret.
From personal experience, ending a long distance relationship can be just as painful as breaking up with someone who lives minutes away, but you can still do it in a way that isn't nasty or cruel - there's no reason to cause him unnecessary pain. There's no easy way to break up with someone regardless of whether or not it's a long distance relationship. Despite that, being kind yet firm will help prevent the situation from being dragged out and can help prevent any additional hurt.