It’s optional, and safe to leave off – plus you save quite a few headaches removing it from wp-config.php. If it’s good enough for PHP.net, Drupal, and Zend, it’s good enough for me.
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It works in 2.5.1 – just make sure the ‘from’ address of your email is the same as one of your blog users (with appropriate privileges) – it will post as that author immediately.
