An email is a component. The same language, compiled for a worse renderer.
$ npm i @frontierjs/email-kit
Table-based blocks, compiled by the same compiler
An email body is written the way a page is, so a designer moving between the two learns nothing new and the components are testable in a browser.
an email build target inlines styles to attributes
Mail clients strip style blocks, so the compiler puts the styles where they survive rather than asking you to write it that way by hand.
Plain-text alternative and the subject, from the component
The three things a message needs come out of one file, so a subject cannot drift from the body it belongs to.
The limits are written down
Outlook’s conditional-comment handling is the fragile part and the package’s docs say so. A compatibility claim nobody has opened in a real client is worth what it cost to write.
Nothing — there is no common equivalent to swap out.
The rest of the stack