I wrote the article below for a readership of edtech companies. But the suggestions would work just as well for any organisation that wishes to keep in touch with its members/clients/visitors etc.
Newspaper by Terry Freedman
Once a school buys your product or service, a newsletter is a great way of keeping them informed of new developments. In this article, we look at what kind of content works well.
If the newsletter is going to be read by teachers, making it a quick read is probably a good idea. If you wish to provide in-depth articles, use the newsletter to link to them on your company blog. (You do have a blog, right?) This suggestion was made to me by Chris Bradford, Product Director at Bee Digital when my own newsletter was starting to rival War and Peace in the long reads department.