[Bug 291171] New: Spam filtering breaks HTML / multipart mail headers on POP3 accounts

[Markus S.]

https://bugs.kde.org/show_bug.cgi?id=291171

           Summary: Spam filtering breaks HTML / multipart mail headers on
                    POP3 accounts
           Product: kmail2
           Version: 4.8
          Platform: openSUSE RPMs
        OS/Version: Linux
            Status: NEW
          Severity: major
          Priority: NOR
         Component: filtering
        AssignedTo: kdepim-bugs at kde.org
        ReportedBy: kamikazow at web.de


Created an attachment (id=67658)
 --> (http://bugs.kde.org/attachment.cgi?id=67658)
Screenshot

Version:           4.8 (using Devel) 
OS:                Linux

This bug may affect all mails processed by external applications, but it's
definitively most visible on spam filtering.
So far the bug only affected my POP3 accounts, not IMAP accounts processed by
mail filtering. (This could just be a coincidence, though.)

KMail seems to blindly set the content type in mail headers to:
Content-Type: text/plain; charset="US-ASCII"

Completely ignoring the individual content types of the two parts in multipart
HTML+plaintext mails.

This is not a bug of the spam filter programs themselves. I tried both
Bogofilter as well as SpamAssassin: Same results.

Technically that bug causes data loss which is why I chose 'Severity: Major
(data loss)'.

Reproducible: Sometimes

Steps to Reproduce:
- Set up a POP3 account.
- Set up the spam filtering via wizzard
- Get multipart HTML+plaintext mails

Actual Results:  
KMail displays multipart mails as source code

Expected Results:  
Do not force 'Content-Type: text/plain; charset="US-ASCII"' and actually
properly render the HTML / plaintext parts

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