[pfx] Re: Detect/extract attachments in broken messages composed by Apple Mail
On 2023-05-26 at 07:05:09 UTC-0400 (Fri, 26 May 2023 13:05:09 +0200) Paul Menzel via Postfix-users is rumored to have said: Dear Postfix folks, Apple Mail violates the standard [1], That's no "standard" that's a Mozilla Inc. bug report. There is no violation of standards here, there is only an *uncommon* MIME structure. resulting in attachments only being shown in the HTML view. How your MUA presents a particular MIME structure is implementation dependent. E.g. my MUA shows me a message with attachments as having attachments, whether it is rendering HTML or not, no matter which part of a multipart/alternative message it is presenting. That's a MUA design choice. This behaviour is to be expected given the incorrect MIME structure of the message. It is: multipart/alternative text/plain multipart/mixed text/html attachment So when selecting the plain part, you don't see the attachment associated with the alternative part. As Viktor noted, this CAN be a legitimate choice. If the "attachments" are images that only exist to be displayed inline in rendered HTML, there's no point in trying to present them in a MNUA that only displays the text/plain part. The message structure should be: multipart/mixed multipart/alternative text/plain text/html attachment If we wanted to detect such messages, and add a notification or extract the attachment, what component would be the right part for such message alteration? A milter? A milter would be the best choice. Both MIMEDefang and MailMunge (a descendant of MIMEDefang) could do this, if you can work with the Perl MIME::Tools module. (I am aware, that this will break with end-to-end encryption (GPG or S/MIME).) It will also break DKIM. Therefore it would be unsuccessful if you were to do this with mail that you want to relay or forward elsewhere. -- Bill Cole b...@scconsult.com or billc...@apache.org (AKA @grumpybozo and many *@billmail.scconsult.com addresses) Not Currently Available For Hire ___ Postfix-users mailing list -- postfix-users@postfix.org To unsubscribe send an email to postfix-users-le...@postfix.org
[pfx] Re: Detect/extract attachments in broken messages composed by Apple Mail
On Fri, May 26, 2023 at 01:05:09PM +0200, Paul Menzel via Postfix-users wrote: > > This behaviour is to be expected given the incorrect MIME structure > > of the message. It is: > > > > multipart/alternative > > text/plain > > multipart/mixed > > text/html > > attachment Note that sometimes the "attachment" in question is specifically related to the HTML part (an image referenced from the HTML or similar). And though in principle the enclosing multipart should then be a "multipart/related", I suspect that might not always be the case in pratice. > > So when selecting the plain part, you don't see the attachment > > associated with the alternative part. > > > > The message structure should be: > > > > multipart/mixed > > multipart/alternative > > text/plain > > text/html > > attachment > > If we wanted to detect such messages, and add a notification or extract > the attachment, what component would be the right part for such message > alteration? A milter? Perhaps "altermime" could do this (though I am sceptical). You'd probably need to write a milter specifically for this (PyMilter). Is this a compelling problem? Perhaps it should be fixed on the sender's end. -- Viktor. ___ Postfix-users mailing list -- postfix-users@postfix.org To unsubscribe send an email to postfix-users-le...@postfix.org
[pfx] Detect/extract attachments in broken messages composed by Apple Mail
Dear Postfix folks, Apple Mail violates the standard [1], resulting in attachments only being shown in the HTML view. This behaviour is to be expected given the incorrect MIME structure of the message. It is: multipart/alternative text/plain multipart/mixed text/html attachment So when selecting the plain part, you don't see the attachment associated with the alternative part. The message structure should be: multipart/mixed multipart/alternative text/plain text/html attachment If we wanted to detect such messages, and add a notification or extract the attachment, what component would be the right part for such message alteration? A milter? (I am aware, that this will break with end-to-end encryption (GPG or S/MIME).) Kind regards, Paul [1]: https://bugzilla.mozilla.org/show_bug.cgi?id=1362539#c3 ___ Postfix-users mailing list -- postfix-users@postfix.org To unsubscribe send an email to postfix-users-le...@postfix.org
