Enter email address twice at checkout option
The option to have customers input their email address twice to check that they match with a script that checks that they match and a prompt if they don't. Its amazing how many people can't type .com correctly and then they wonder why they don't get any notifications.
Dave Nelson commented
I don't like it. This will result in more abandoned carts. Instead implement a standard publicly available regex email address validity check. Google it.
The possible WA solution is something like