I code HTML emails and paste them into our ESP's "code editor" to send. We recently discovered that even though our ESP has a 'Send as Multipart' choice, to add a plain text version to the email, the plain text client in Litmus shows nothing.

So, I have been trying to discover how to code plain text into my HTML emails. What I have been able to find (Content-Type: multipart/alternative, then the boundry sections) looks like it's meant to be written into a program, like when sending an email from JavaScript, PHP, C#, etc. I tried sending a message coded that way to Litmus and just got a big blob of text at the top of the HTML. Sigh.

I'm hoping someone here may be able to tell me how to encode plain text into the HTML. Or, if we are at the mercy of an ESP that doesn't quite work. I've read advice here that the plain text version should be edited for clarity after (something else?) generates it. That leads me to believe it's possible, but what do I know.

Thank you much in advance for any advice you may have!