In the world of email marketing, prevailing wisdom is that bigger is better — at least when it comes to the size of your subscription list. The more people who receive your messages, the better, right?

While there is a certain amount of truth to that statement, a list with thousands of subscribers isn’t going to do you much good if 90 percent of them aren’t engaged.

The fact is email lists are living things. They are in a constant state of flux, with new subscribers being added and others leaving all the time. Recipients’ interests and preferences change over time as well, and if you aren’t keeping up, you could be unintentionally derailing your own marketing efforts.…