Offer relevant content. When you send an educational email, you’re trying to build a relationship with your customers. The best way to do that is to teach them something. However, you want to teach them something that has a connection to your business. For instance, Monster.com, the job search site, sends its customers information about life in the workplace. An example is below.
Human spam filters are even more complex. No one can tell you exactly what makes someone click the spam or abuse button, but there are some general rules. You’ll want to avoid buying lists or sending emails without explicit permission, being vague about when you’ll email, hiding the unsubscribe option or making the process of unsubscribing unnecessarily difficult, or leaving unengaged, inactive leads or customers on your list (though, you can and should eventually mount a reactivation campaign for those inactive leads).
Look for a point of diminishing returns. Where are your campaign investments providing value? At Marketo, inbound strategies like content marketing are the strongest channels, and should be maximized to a point; but beyond that, inbound tactics need to be supplemented with outbound, paid channels in order to create sustainable demand and generate new leads from your website.