You need to have a paid account, make sure you're logged in then go to livejournal.com/manage/emailpost.bml for all the info you'll need! Essentially, you set a PIN number which must be included in the email, prefixed with a + and you email to yourusername@post.livejournal.com, after listing which email addresses can post to it (so your journal can't be posted to by just *anyone*).
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Stu xxx
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