When attaching a file to a message (composing a new message), the
MIME type of the attached file is choosen based on the file extension
from the mapping list defined in the mime.types file(s).
Sylpheed defines its MIME type mapping table by loading the
system wide MIME types file, then the user file.
The systeme file is SYSCONFDIR/mime.types (SYSCONFDIR can
be defined a compile time), or if it does not exist, /etc/mime.types.
The user file is $HOME/.sylpheed/mime.types.
A mime.types file consist of one MIME type definition per line,
each definition line starting with the name of the MIME type, followed by
a space separated list of the corresponding file extensions.
The file can contain empty lines, and comments start with the #
character and close at line's end.
Following is a typical mime.types file (an extract of mine):
# This file controls what Internet media types are sent to the client for
# given file extension(s). Sending the correct media type to the client
# is important so they know how to handle the content of the file.
# The Internet media type registry is at
# ftp://ftp.iana.org/in-notes/iana/assignments/media-types/.
# MIME type Extension
application/mac-binhex40 hqx
application/mac-compactpro cpt
application/msword doc
application/pdf pdf
application/postscript ai eps ps
application/rtf rtf
application/x-bcpio bcpio
application/x-bzip2 bz2
application/x-csh csh
application/x-gtar gtar
application/x-gzip gz tgz
application/x-kword kwd kwt
application/x-kspread ksp
application/x-kpresenter kpr kpt
application/x-kchart chrt
application/x-latex latex
application/x-sh sh
application/x-shar shar
application/x-shockwave-flash swf
application/x-tar tar
application/x-tcl tcl
application/x-tex tex
application/x-texinfo texinfo texi
application/x-troff t tr roff
application/x-troff-man man
application/zip zip
audio/mpeg mpga mp2 mp3
audio/x-aiff aif aiff aifc
audio/x-wav wav
image/gif gif
image/ief ief
image/jpeg jpeg jpg jpe
image/png png
image/tiff tiff tif
text/plain asc txt
text/rtf rtf
text/sgml sgml sgm
text/xml xml
video/mpeg mpeg mpg mpe
video/x-msvideo avi
text/html html htm
If the file can be found or has the wrong format, Sylpheed will assume
the default MIME type for all the attachments: application/octet-stream.
In such a case, the recipients mail client may not know what application
to use to view the attachment.
When opening an attachment (select the attachment, right click and select
Open) Sylpheed uses one of the following methods to determine
the application to launch:
The attachment is an image: the application is the one defined by the
mime_image_viewer variable of the common preferences configuration
file ($HOME/.sylpheed/sylpheedrc). If no application is defined, or
if the format of the definition is not valid, the default application
command is display (ImageMagick viewer).
The attachment is a sound file: the application is the one defined by the
mime_audio_player variable of the common preferences configuration
file ($HOME/.sylpheed/sylpheedrc). If no application is defined, or
if the format of the definition is not valid, the default application
command is play.
The attachment is a HTML file: the application is the one defined by the
uri_cmd variable of the common preferences configuration
file ($HOME/.sylpheed/sylpheedrc). This can also be changed in the
Common preferences, by changing the Web browser defined
in the Other tab.
Any other attachment type: Sylpheed relies on metamail to use
the correct application (Sylpheed starts metamail giving it
the attachment file and the MIME type taken from the mail).
The binding of the applications to each MIME type is defined in the
mailcap file. The systeme wide file is /etc/mailcap,
while the user file is $HOME/.mailcap.
In the mailcap file, there is one definition per line, big lines
can be broken by escaping the newline with a \ character,
the first element of the line is the MIME type, then a semi-colon,
(;), and finally the application to launch.
The application part (right side of the semi-colon) can contain several
shell commands separated by an escaped semi-colon (\;) and
the %s string is replaced by the name of the file when
launching the command.
Following is a typical mailcap file (an extract of mine):
image/*; ee %s
video/mpeg; gtv %s
video/*; xanim %s
application/pdf; xpdf %s
text/html; dillo %s