The whole point of e-newsletters (and blogs) is so that when your readers need you, they remember you (hopefully in a good way) and will find you easily. They can call you up or email you to hire you, or buy your products and services.
Michael Katz of Blue Penguin writes about this in his recent ezine (always a fun read). He calls it Identifiability:
"Although apparently not a real word, this sums up an important aspect of being remembered. Because if I’m going to call you or pass your name along to a friend in need, you’ve got to pop into my head the moment someone mentions a desire for "blank" (with blank being whatever it is you do).
"…If your blank is clear and narrow (e.g. "Restaurant marketing guru," or "Financial planner for female small business owners," or "Bald, but oddly likeable E-Newsletter expert") you’ve got a good chance of coming to mind.
"If, on the other hand, you’re associated with a more generic label (e.g. "life coach" or "management consultant"), you’ll be competing with many more people, one of whom (rather than you) may pop into my head when I start thinking about who might fit the bill."
This means that you have to claim a narrow piece of your industry. Decide what you want to be famous for. You may think that you are reducing your reach, but it is actually increasing the likelihood of people remembering you.
This is the power of niche marketing and the branding associated with it. Become easily identifable, easily recognized, and specifically niched. Then when you regularly send out an emailed newsletter, you are staying in the minds of readers. By doing so, readers will turn into clients. Which is the whole point, remember?