How can you translate the content of emails?

In order to translate the bulk of the email content, you can just enter the content into the email editor field itself.

In addition to that, there is some content that is auto-generated, such as the content in the footer of the email and some dynamically generated text such as "this/these" which is generated automatically based on how many items are in the cart at any given time. This content is controlled by the language setting under Configuration:

If your site's language isn't included there, you can add it to this  spreadsheet and let us know once that's done, so that we can incorporate that into the settings.