.

If you aren't testing, then you are just guessing, which is poor business practice.

Use Google Experiments.  This is a brilliant and powerful tool for increasing your ROI (use this YouTube video as your introduction)

1. Test something every time

   Testing is a classic way for direct marketers to refine their efforts to get the best results. If each of your email campaigns doesn’t include a testing component, you’re missing out on an opportunity to improve your ROI. Some elements you may want to test include:
   
   

   • Subject line
   • Message
   • Call to action
   • Day of week sent
   • Time of day sent
   • Landing page
   • 'From' line
   • Offers
   • One segment of your existing list against another

   Your results will provide new ideas for more effective campaigns and help you get rid of offers, lists or creative that aren’t working.
   
   

2. Why testing is mandatory.
   
   
3. Eight steps to a successful email test.