To reproduce: Received a message with a few PDF attachments. Actual results: I can see attachments when I look at the email in the Message Pane, but there's no corresponding icon in the Attachments column in the message list. When I filter view by "Has Attachments" the message in question is not included! Expected results: I should be able to see which messages have attachments and expect to find them with the appropriate view filter Additional info: If I open the message explicitly (not just in Message Pane), the attachment status is updated to correct value. If I then "Repair" the folder, attachment status is reset to the problematic status Setting Severity to major since messages appear lost to the user

Reopen per bug 953315 comment #11 and bug 953315 comment #12. Mail structure provided by bug opener of this bug at bug 953315 comment #10. > Content-Type: multipart/alternative; boundary=Apple-Mail-8--745298500 > --Apple-Mail-8--745298500 > Content-Type: text/plain; charset=windows-1252 > --Apple-Mail-8--745298500 > Content-Type: multipart/mixed; boundary=Apple-Mail-9--745298500 > --Apple-Mail-9--745298500 > Content-Type: text/html; charset=us-ascii > --Apple-Mail-9--745298500 > Content-Disposition: inline; filename="2015-02-01 [***] Minutes.pdf" > Content-Type: application/pdf; > --Apple-Mail-9--745298500 > Content-Transfer-Encoding: quoted-printable > Content-Type: text/html; charset=windows-1252 It looks for me following. 1. multipart/alternative => text/plain is used as "message body part under multipart/alternative". And, multipart/mixed under multipart/alternative != usable part such as text/plain, text/html under multipart/alternative. So, it should be completely ignored, because text/plain part is already chosen in multipart/alternative. 2. However, it's multipart/mixed, then "application/pdf part under multipart/mixed under multipart/alternative" is shown as-if attachment at attachment box, because it's non-used/non-displayable sub part. If such PDF part is shown as-if attachment, I believe text/html part also should be shown as-if attachment. Or, it may be: 3. "multipart/mixed under multipart/alternative" is treated like multipart/related because text/html is contained. 4. text/html in "multipart/mixed under multipart/alternative" is treated as "message body" 5. PDF part in "multipart/mixed under multipart/alternative" is shown as-if attachment because non-displayable. 6. Because it's not "non-used sub part under multipart/related", "attachment icon" is not shown at Thread pane.

It's hard for me to say "malformed mail" in this case. Interpretation of multipart/mixed depends on people, mailer, mail application etc. (1) Traditional use(or old definition) : message body(text) + attachments (2) Current definition by RFC : Show content in order placed under multipart/mixed, with respecting Content-Disposition:inline/attachment requested by mail sender. There is no "message body" concept in this case. I think (2) is better applied on "multipart/mixed under multipart/alternative", at least when text/plain and/or text/html is contained in the "multipart/mixed under multipart/alternative". When provided mail structure, I think following is valid procedure. 1. Because text/html is contained, accept the multipart/mixed as "Thunderbird can display it" part in multipart/alternative. 2. Because multipart/alternative, choose the multipart/mixed which is located at bottom(highest preference of sender). 3. Show sub parts in the multipart/mixed in order placed in the multipart/mixed, with respecting Content-Disposition:inline/attachment requested by mail sender. 4. Because PDF is non-displayable part, show it in Attachment box, as "valid attached file to mail".