There's no sense spending all that time designing, coding and writing your email newsletters, only to get them trapped in your recipients' junk folders. Make sure your newsletters go straight to your subscribers' inboxes by learning how spam filters think. Spam filters look at a long list of criteria to decide whether or not your email is junk. The list of spammy criteria is constantly growing and adapting, because spam filters learn more about what junk looks like every time someone clicks the This is spam button. Spam filters even sync up with each other to share what they've learned. There's no magic formula, but these tips will help you avoid common mistakes that often send email marketing to junk folders.