You should be writing your newsletter for a specific audience. Select 20 random people from your newsletter list and give them a call a week after you send out your newsletter. Ask them what they remember about it. Do they remember getting it? Did they skim it or read certain articles? What do they like best about it? What sections do they ignore? What other suggestions do they have? Look for trends in the replies you get.

If you want to go beyond anecdotes, you can conduct a more formal survey. SurveyMonkey is a good online tool. Advertise the survey in your newsletter and offer a prize drawing to encourage people to complete it.

You should also set goals for your newsletter as part of your larger communications strategy. Evaluate how well your newsletter contributes to that strategy. Do donations go up after it comes out? Do people mention the newsletter to you? Do event registrations go up?