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For information on mime and mime type lookups
(as well as default application associations)

Basic Desktop Mime Handling https://antofthy.gitlab.io/info/misc/mime.txt
Mail mime attachments       https://antofthy.gitlab.io/info/mail/mail_attachments.txt
Desktop Application files   https://antofthy.gitlab.io/info/apps/Desktop.txt
Gnome Applications          https://antofthy.gitlab.io/info/X/Gnome.hints

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The OLD ".mailcap" file...

The ".mailcap" file  was used only by mail handlers only.

file format
   mime/type;  application "%s"


To have it use the modern system use...
   */*; xdg-open "%s"

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Mail Attachment Using sendmail!
(whole mail, not as an attachment)

( echo "To: to@address"
  echo "Subject: hello"
  echo "Content-Type: text/html"
  echo
  cat test.html

) | /usr/sbin/sendmail -t

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Mail Attachment using mutt

  mutt -e 'set content_type=text/html' -s 'My subject' me@my.com < msg.html


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Mail Attachment Using xdg-email  (and setting a "mailto:" handler)

Example...

  xdg-email --subject "Test Dragon" \
            --body "Attached Dragon" \
            --attach icons/dragons/Silly_Dragon.jpg \
            Anthony.Thyssen@gmail.com

This creates a mail which is then opened using a "default mail app"
This is defined in mime appliactions "~/.config/mimeapps.list"
  x-scheme-handler/mailto=claws-mail.desktop

WARNING: The xdg system does not understand multiple default appliactions
on a single line.

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Mail Attachment Using mhbuild

Add attachments to the mailfile (with headers)

   #image/x_png; name="arc.png" arc.png

Then filter in VI using...

   :%!mhbuild -

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General Mail Mime Attachment handling

Attachment Filename
  The file name must be added to the "Content-Type:" line of the
  attachment.

  EG: ------- =_aaaaaaaaaa0
      Content-Type: application/octet-stream; name=".plan"
      Content-ID: <10662.1005524452.1@kobold>
      Content-Transfer-Encoding: base64

Boundary Lines
  Note that two extra "-" are prepended to the actual boundary lines
  to the bundary marked given in the header of a mime mail.

  EG: In the header you have...

     Content-Type: multipart/mixed; boundary="----- =_aaaaaaaaaa0"

  In the body you have...

      ------- =_aaaaaaaaaa0

  The header has 5 "-" characters but the actual boundary line has 7.


Example...
  To: user@example.com
  Subject: sending an attachement
  MIME-Version: 1.0
  Content-Type: multipart/mixed; boundary="----- =_aaaaaaaaaa0"
  Content-ID: <10662.1005524452.0@kobold>

  ------- =_aaaaaaaaaa0
  Content-Type: application/octet-stream; name=".plan"
  Content-ID: <10662.1005524452.1@kobold>
  Content-Transfer-Encoding: base64

  CkFudGhvbnkgVGh5c3NlbiA8YW50aG9ueUBjaXQuZ3UuZWR1LmF1PgogIFdXVyBIb21lIFBh
  Z2U6ICAgICAgIGh0dHA6Ly93d3cuc2N0Lmd1LmVkdS5hdS9+YW50aG9ueS8KICBKb2IgRGVz
  LS0tCgo=

  ------- =_aaaaaaaaaa0
  Content-Type: text/plain; charset="us-ascii"
  Content-ID: <10662.1005524452.2@kobold>

  Anthony Thyssen ( System Programmer )
  http://www.cit.gu.edu.au/~anthony/

  ------- =_aaaaaaaaaa0--

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