Drupal - How to customize order confirmation e-mail

Order receipt emails are powered by Twig templates, just like regular pages. This helps us avoid the inflexibility of tokens and their lack of conditional support ("Only show the Shipping information heading if the token has data"), which were big problems for D7 sites.

You can override the commerce-order-receipt.twig.html template in your theme to customize it.

See https://github.com/drupalcommerce/commerce/blob/8.x-2.x/modules/order/templates/commerce-order-receipt.html.twig

The docs page is obviously still a work in progress (as in, it's stubbed but has no real content at https://docs.drupalcommerce.org/commerce2/developer-guide/orders/customize-order-receipt-emails), but the basic idea is we depend on Swiftmailer for sending HTML e-mails and expect developers to override the default e-mail template we provide. Keep an eye on those docs, as we'll be fleshing them out during DrupalCon week. If you end up with a successful customization, would love to see a blog post about it that we can share with others! : )