You split your email subscriber list into “cold” vs. “warm” leads so you can compare similar groups of customers in this test. You prepare two versions of your email—one with the normal subject line, and one with a much shorter, punchier subject line. You send half of your cold leads the normal subject line and half of your cold leads get the new, exciting subject line. You also send half of your warm leads the normal subject line, and the other half get the new subject line.
Full-funnel campaigns also take into consideration how the marketing funnel has morphed over the years. The old school of thought had a top, middle, and bottom part of a funnel, where customers went in at the top and left it after making a purchase. The funnel has evolved into a customer lifecycle that includes those pre- and post-purchase phases mentioned earlier.
Everyone's busy and their inbox is already full. Why add to the problem with a longwinded email? People generally like short, concise emails better than long ones because concise emails have an obvious focus. Plus, when your users are scanning through all their emails in a short amount of time, they're more likely to find the overall message before deciding to take any action.