Want to improve response to your fundraising emails?
The most important element to work on is the subject line. When you don't get a winner there, it really doesn't matter how brilliant the rest of your work is.
Strange thing about subject lines: There are two contradictory "tricks" to win eyeballs. You can read about them on the Bloomerang Blog, at Fundraising Magic Tricks to Boost Year-End Response.
Trick #1: Clarity. Use the subject line to tell the recipient exactly what they'll find inside.
Trick #2: Curiosity. Create mystery. Don't reveal what they'll find inside.
In my experience, #2 is the go-to approach most often. #1 works better only when the thing you're revealing is either an amazing "deal" or some situation everyone is thinking about -- like a natural disaster.