To solve a problem where SMTP servers won’t display attachments with emails that have content-type set to multipart/alternative, I’ve had to set the email to multipart/mixed, but this has the unfortunate side-effect of displaying both the plain text and the HTML, which create pointless duplication and is unsightly to the user.
With multipart/mixed set, is there any way to hide ‘text/plain’ (without removing it as it’s going to be used by a parser) from the user and just display the HTML? I am referring only to hiding it for cilent programs (such as hotmail, yahoo, etc) and not IMAP etc where the user can see everything.
If you don’t want the text displayed to the user ever, then including it as part of a multipart/mixed message seems like the wrong thing, as the contents of your text/plain part is more correctly metadata. I’d probably put it in a header or something if you can.
If it must be part of the multipart message, I’d try testing using a custom mime-type that a mail client doesn’t know about, and see if that causes the section in question to be hidden. This feels a bit hacky, but it could potentially work.