"While the email newsletter model has changed and adapted to the times, it’s continued to thrive. People love curated content, and they appreciate the lean-back experience of having interesting information delivered to them." Pete Sheinbaum the former CEO of Daily Candy offers some guidelines.
It's like the old direct mail pieces, really. Numbers & call to action matter as much as content.
Build a successfull newsletter just with these 4 basics:
Entertain and inform
Be brief
Stick to one topic
Leverage non-email channels for delivery
This article will be helpful because many entry level jobs in PR requires you to write newsletters, news releases, media advisorys, etc.