Re: [Bug-mit-scheme] imail: mystery of the invisible attachments

[Taylor R Campbell]

   Date: Mon, 18 May 2009 21:17:53 -0400
   From: Julie Sussman <address@hidden>

   This is not the first time I have failed to see attachments from an
   Apple sender, but I don't think I kept other examples.  I wonder if
   this is some problem of nonstandard messages created by Apple Mail.
   Perhaps you've told me about this problem before, and I forgot.

Yes, I've seen this several times: it's a bug in Apple Mail.  You can
work around it by setting `imail-mime-show-alternatives' to #t.

Some background, if you're curious:  Some messages are sent with the
same content in multiple alternative formats, such as plain text and
HTML, so that those who just want to read the actual message can do
that, and those whose who want to see the obnoxious colours drowning
out the content can do that.  Such messages are called multipart/
alternative messages, and the parts are meant to have identical
content, so that there is little value in displaying more than one of
the parts; hence, by default, IMAIL shows only the plain text part.

The bug in Apple Mail is that it sometimes (and I don't know under
what circumstances precisely) sends attachments as parts of a
multipart/alternative message, even though the attached files
certainly do not have content identical to the plain text of the
message.  Fortunately, setting `imail-mime-show-alternatives' to #t
causes no harm other than making IMAIL occasionally show parts that
might look like attachments but are really just HTML equivalents of
the plain text that IMAIL shows in-line.