There are certain obvious email marketing no-nos to avoid, if you want to stay out of the spam folder – things like mentioning Viagra, or writing in all caps. But spam filters are much more sophisticated now than they used to be, so one or two trip-ups usually won’t mean the end for you. The best way to stay out of the dreaded spam folder is to write not like a salesperson, but like a friend – the tone of your emails, and even the vocabulary you use, will automatically be different.