If you want to remain out of the spam box, there are a few apparent email marketing no-nos to avoid, such as referencing Viagra or writing in all caps. However, spam filters are far more sophisticated now than they were in the past, so a couple of missteps typically won’t spell the end for you. The easiest approach to avoid the spam folder is to write as if you were writing to a friend — the tone of your emails, as well as the terminology you use, will naturally be different.