Give people a way to avoid more emails about the same offer. If you do a concentrated promotion for something, you might send lots of emails about it in a short time. Give people the option to avoid future emails about the offer. Just add a link to the end of the emails (e.g., “If you’re sure you’re not interested in [ offer ], click here, and I won’t send you any more emails about it this year.”). That way you won’t annoy people who aren’t interested in the offer now. You could argue that some of them might buy if they saw all the emails. Well, if you’re only interested in this month’s sales, send as many emails as you can. I just assume you want to have someone left on your list for next month.
Bloggers are the most obvious example of focusing on this email marketing strategy almost exclusively. SaaS (Software as a Service) businesses are another group that typically heavily emphasize content emails. Of course, bloggers, SaaS businesses, and everyone else can send content emails while also using the other email marketing strategies. And you should do it, too.

That isn’t to say that sales-y promotions couldn’t ever create results—as marketing “gurus” have proved. The results just aren’t as good as they could be. Take the biggest gurus’ results—the ones they boast about—and calculate their conversion rates. Often their marketing is comparatively ineffective. They just have massive volume, so the sales numbers are impressive.