Which is more important for Apple Watch emails?
1. the sender
2. the subject
3. or the first part of the email content, called the "pre-header"?
Most email marketers would say it's the subject. They may even spend effort on A:B testing to choose the best subject. But look at how much space is used for each, and you'll see the pre-header is more important. You should A:B test that first.
The same is true of older email clients. Look below for how your customers see your emails in a typical in-box, when they are deciding whether to click. This example is from Yahoo, but others including Gmail are similar.
Again, about half of what customer see is the pre-header, but marketers use this surprisingly badly. I've drawn boxes around the useful content in the pre-headers - that which makes customers more likely to open - and note how little there is! Many senders are wasting valuable marketing space by repeating the subject or showing irrelevant instructions.
I'm sure that you are doing better - but if not then make this week's main task perfecting your emails for the in-box. (Here's some basic technical advice).
Once you have set up a pre-header, you can make it work harder by personalising it for each shopper, using their details and real-time triggered analytics. For example cart and browse abandonment emails are even more effective if you jog the shopper's memory by including the name of an abandoned product in the subject or pre-header.