we send the email out early to four separate batches of ~80,000 readers
each batch gets a different subject line
whichever one has the highest open rate goes out to the remaining 1.8 million readers
we just skim the newsletter stories for interesting and eye-catching phrases
then one writer picks them for the day and we roll with whatever they choose
the perfect blend of:
-art (just pick cool sounding phrases)
-science (we do A/B test)
-trust (any writer can pick them on any day)
still havent been given an adequate explanation of why that is lol