In order to maximise your Open Rate, you might want to test different subject lines and send the one that your subscribers liked the most.
For Newsletters you are able to send 2 different subject lines to a small number of your recipients in order to test them, then SmartrMail will send the best one to all your subscribers:
Click on A/B test
Enter the two subject lines you want to test
Enter the test size (i.e: 20% will send subject A to 10% and subject B to 10%)
Enter when you want that test to end (i.e: 3 hours)
Once the test period is finished, the remaining emails will be sent with the winning subject line.