WordPress Tutorials: "Overview:

WordPress uses the 'secret address' method to post by email. You have to create a new email address on your web host's mail server, and then change some settings in WordPress. You also have to regularly check the page wp-mail.php for new mails to post to the blog. You need to create a sufficiently secretive email account to prevent the possibility of SPAM messages being posted on your blog. This is also addressed in this How-To."