I'm still working my way through e-mail, which has been about 95% enjoyable so far. The other 5%, well . . . I try to see it as a writing challenge. I mean when someone takes the time to tell you that you're going to burn in hell, the least you can do is assure them that you'll save a spot for them.
Honestly, I think we writers are too serious when we answer hate-mail. Yes, it's polite to say things like I'm so sorry you didn't enjoy the novel and I appreciate the feedback but you know you're lying and they know you're lying. At some point in the hate-mail they tell you that they're not going to buy any more of your books. So, why don't we ever have a little fun with them?
Reader: Apparently you know nothing about writing good books.
Author: No, they only pay me enough to write bad ones. Think you can get me a raise or something?
Reader: Did you have to end the series like this?
Author: My editor wouldn't let me publish the version where I blow up the Earth and everyone dies.
Reader: How could you kill that dog/cat/defenseless animal in your story like that?
Author: Because if I did it to real ones they'd arrest me.
Reader: I can write a better story than you!
Author: Yes, but how are you at selling it to clueless publishers who only print crap? Huh? Huh?
Reader: I hated your love scene. It made me sick.
Author: Gee, I practiced that one myself first, and your husband seemed to love it.
Reader: I should give up reading books if they're all as stupid as yours.
Author: I asked all the other authors and they said, yes, they are. So yes, you should.
Reader: I'm writing a letter of complaint to your editor.
Author: Good. While you're at it remind that bitch she still hasn't paid me D&A on the last manuscript, and mention that my ketchup and beans are about to run out.
Reader: No one should be allowed to publish stories like yours.
Author: They're not. It's called plagiarism.
Reader: What a terrible writer you are.
Author: Oh, that's nothing. You should hear me sing. Really. What's your phone number?
Reader: Your book sucks!
Author: Maybe you could use it as a little vacuum for your car.