Empty `HtmlBody` for some Apple Mail messages (sent from iOS)

[alex-jitbit]

Describe the bug
Both HtmlBody and TextBody return null for some Apple Mail messages. However the bodies can be retrieved by enumerating BodyParts manually like this:

body = ((TextPart)msg.BodyParts.FirstOrDefault(b => b is TextPart && b.ContentType.MimeType == "text/html"))?.Text;

• MimeKit Version: 4.2.0

To Reproduce
I've attached an .eml file and cleared out all the sensitive info from it.

Expected behavior
HtmlBody should be set to first BodyPart maybe?

Additional context
I totally understand that the message hierarchy is kinda, uhm, malformed. However maybe you would like to add a workaround b/c this is from iOS 16 Mail app which is becoming popular.
test321.zip

[jstedfast]

I've taken a look at the message and it appears that the mime structure is as follows:

• multipart/alternative
  • multipart/mixed
    • text/html
    • text/html
    • text/html

It's a pretty bizarre structure that I'm not entirely sure how to interpret.

Expected behavior
HtmlBody should be set to first BodyPart maybe?

Maybe? Technically speaking, the entire multipart/mixed is the "body". Each child of a multipart/alternative is supposed to be an option to use as the message body, each being an "alternative" to its siblings. In this case, the multipart/mixed is the only child of the multipart/alternative.

[jstedfast]

This is fixed now.