The second order is the whole game.

Was the order right, was it on time, was the food still good on arrival. Those three account for most of the decision, and no email fixes a cold delivery. This is why restaurants with a retention problem should look at their operations before their marketing: you cannot message your way out of a bad first experience.

There is a period after a good first order where somebody is receptive, and it is roughly their natural reorder gap for that kind of food. Miss it and you are competing again with every other option. A prompt inside that window works. The same prompt two months later reads as an ad.

One message, shortly after the natural window opens, referencing what they ordered. A small incentive helps for a second order specifically, because it is the highest-value conversion you will make and it only has to be paid once. After the second order, stop incentivising: the habit is what you were buying.

A short question to customers who ordered once and never again is uncomfortable and unusually informative. The answers are rarely mysterious: it arrived cold, it took longer than quoted, an item was missing. Those are all fixable, and none of them would have shown up in your sales figures.

A share of first-time customers were never going to return: visitors, people trying somewhere different once, people who did not like the food and never will. Chasing every one of them wastes effort. Fix the mechanical failures, prompt once, and accept a floor.