Support for alternative parts other than text/plain and text/html

[Mike Dillon]

We have an application that sends out emails with the following structure:

• multipart/alternative
  • text/html
  • text/calendar

This mimics the style of emails sent out by Outlook, allowing invitation emails to be sent (and canceled) from a Rails application with native Outlook "Approve/Tentative/Decline" buttons.

I wanted to use premailer-rails to allow us to easily style these emails, but unfortunately it munges this email and drops the text/calendar part when it adds the text/plain part. I think I could probably get it to work by disabling the generation of the text/plain part, but I ended up falling back to inline styles and removing premailer-rails for the moment.

It would also be good to deal with messages that are structured similar to how Google Calendar structures its invitation emails:

• multipart/mixed
  • multipart/alternative
    • text/plain
    • text/html
    • text/calendar
  • application/ics

[Philipe Fatio]

Thanks for your input. Indeed, premailer-rails is a bit naive about this, judging by a quick look at the code. I think it simply grabs the text/html part and replaces it by a multipart/alternative that contains a text/html and a text/plain part.

[Jordan Kicklighter]

This would be great for another reason as well: if you don't want to rely on premailer to generate the text/plain portion, there is no way to do this. Premailer clobbers whatever plaintext you may have created in ActionMailer.

[Philipe Fatio]

PRs welcome ❤️