Looking to see how to test your email subject lines?
It can be as simple as this example from ASOS that mistakenly appeared in my Inbox
But here are a few other ideas / tips
Length. I've usually found that shorter, to the point is better. Your audience may be different
Do versus Say. Does your audience react better to actionable or informative headlines?
Search and Copy. What's your audience searching for using Google or perhaps on your own website ?
Be careful what you wish for
'Why does the subject line including the free offer get more opens than one without but then the clicks remain the same?'
Getting your audience to open the email is not the end game. Your end game is always the ultimate conversion whether that be a sale, whitepaper download or an event booking