I also work for a not for profit organisation and we have recently done our first electronic mail out. It was interesting to note that only a tiny percentage of those people who we had added to our database 'because we could' rather than because we had a relationship with them even opened the email. Of those a large percentage unsubscribed and an even larger percentage didn't click to read any of the articles.

People who had had previous dealings with us, and had developed a relationship with us, were keen to open and read our mail out, with the majority doing so.

I would highly recommend 'opt in' email lists for current & interested customers.