Within Mailchimp you can split test a list with a small set of data from your list. Mailchimp will then automatically send the bulk of your list to whichever the winner is (email with the highest open rate) from the split test. This isn’t possible in Online Express without manually splitting your query list into 3 lists (2 small lists for split testing and 1 with the bulk email), then manually looking to see which list was the winner then manually sending the bulk email to everyone to look like the winning email. If you could split test in Online Express this would allow us to use Online Express email function.