While skimming the source code of org-mime I noticed two severe issues
with regards to the MIME specifications:

  - when creating an attachment for a image org-mime (still) uses the
    file extension as MIME media subtype for Gnus messages. This not
    in compliance with RFC 2046.  As mentioned before org-mime
    should/could use the function to determine MIME media type of
    message-mode and mime-edit-mode respectively.

    For SEMI the function is `mime-find-file-type', called with the
    file name as argument and returns a list whose first element is a
    string with MIME media type and second element is MIME media
    subtype.

  - when creating an attachment for a image org-mime uses the path to
    the image for the value of the content-id header.  This violates
    RFC2045, section 7.

    The value of the content-iD header field is syntactically
    identical to the message-id header.

    addr-spec   =  local-part "@" domain

    For SEMI the function for creating a message-id string is
    `wl-draft-make-message-id-string' that is called without any
    argument and returns a shiny new message-id header field value
    /with/ the angle brackets.

Furthermore there are some minor glitches:

  - the "filename" parameter is only defined for the
    content-disposition header field; because images are attachments
    they can/should be easily send with

    content-disposition: attachment; filename="<filename>"

    For SEMI (replace _ by -):

    __[[type/subtype
    content-disposition: attachment; filename="<filename>"][base64]]

  - org-mime uses `reporter-compose-outgoing' to open a new message
    draft.  This is not a could solution because (a) org-mine does not
    want to send a bug report and (b) would depend on reporter.el
    without necessity.

  - org-mime /should/ add information to the user-agent mail header
    field indicating that the message was created with the help of
    org-mime.

HTH
 -- David
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