Their email marketing strategy and plan was to optimise their email subject lines because this was the first place that their customers would engage with. To do this, they used an AI generating subject line tool called Phrasee. There are plenty of increasingly sophisticated AIs out there which can do this kind of thing. Phrasee worked for Dominos because it capitalises upon being specific to brand voice, and is optimised to drive action.
Activation: A new user creates an account but, they do not use your product within the first 7 days. Create an  “activation” campaign that sends an automated email with their login information, steps on how they can get started and include a video demonstration for additional support. You can also invite them to a one-on-one meeting to walk them through the product and answer any questions they may have.

When you're using email as a marketing tool, you're working on a pretty personal basis. This isn't ‘drive-by' stuff -you're directly targeting customers from their inboxes. There's a huge amount of potential which comes with this kind of marketing... but you'll only reap that potential if you REALLY understand both the marketplace you're operating from, and the audience you're talking to.