Here's a sample McSweeney's email rejection, which I rather appreciate:
McSweeney's thanks you for your recent submission. We rely on submissions like yours, and a good portion of what we publish comes unsolicited, through the mail.
Unfortunately, we can't find a place for this piece in our next few issues. Nevertheless, please feel free to submit more work in the future. Our themes and tastes change.
Thanks again for your efforts and for letting us see your work.