Don't just send email blindly!
Adapt to your audience. Know your constituents. Are they over 40? Young and active? Business professionals? Alumni who like sports? Examine which emails get the best response by examining the articles and links which get the highest counts in your reports. Ascertain what your audience is interested in and adapt your next campaign to this response.
Email is a moving target, and so is your audience. Know them and adapt. Your metrics will improve!