A couple of days ago I read an excellent and easy post about customer newsletters named 'Your Most Powerful Marketing Tool - A Customer Newsletter' written by Tripp Braden (@TrippBraden). I so agree with the text (cut from the post) "Newsletters are cheap, they provide valuable information, and they keep your name in front of your customers, prospects, and former customers."
I think a customer newsletter is a really strong market tool because of the ease creating, writing and publish, also because of the low cost. Of course as long as it is in a friendly layout and with a good content. Unfortunately I see to many uninteresting newsletters which I delete immediately.
At TeleComputing we send out newsletters quarterly. It might be too seldom and that a monthly would be better but it how it is for the moment. We focus on writing basic general articles about new services, business, trends etc and have always as a start the MD-words and end it with an interview with one of our employees. We never do it too "selly", then the receivers for sure would delete it. They want good information from their service provider and not the feeling that they have to buy things, even if the main goal for the sender in the end always is to get more business and to be seen on the market.
I think the trick to get readers, and business, from your newsletter is to embrace quality before quantity, but of course with a high quantity of receivers.
I'm sure our cost isn't as low as Tripp says, 0.89$ the send out, but it's definitely less expensive than to do print outs, which appeal to Green IT and definitely to cloud because it can be read from any device any time.
Inspiration (in Swedish, but you can get a good idea of a successful layout and context): TeleComputing News