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   1 .TH MH\-MIME %manext7% 2014-12-15 "%nmhversion%"
   2 .
   3 .\" %nmhwarning%
   4 .
   5 .SH NAME
   6 mh\-mime \- overview of nmh MIME message composition and display
   7 .\"
   8 .SH DESCRIPTION
   9 The acronym MIME stands for Multipurpose Internet Mail Extensions, the
  10 format of Internet messages used to send multi-media content.
  11 The
  12 .B nmh
  13 command suite has support for the display and composition of MIME messages, but
  14 currently MIME support is not completely integrated into all tools.  This
  15 document provides an overview as to which tools support MIME message display,
  16 storage, and composition.
  17 .SS
  18 Local Character Set Conversion
  19 All of the
  20 .B nmh
  21 commands convert non-native character sets to the local character set,
  22 as specified by the operating system locale settings.  See
  23 .IR locale (1)
  24 for more details on the environment variables used to set the
  25 local character set.  Character set conversion will only take place if
  26 .B nmh
  27 was built with
  28 .IR iconv (3)
  29 support.  See
  30 .IR mhparam (1)
  31 for how to determine whether your
  32 .B nmh
  33 installation includes
  34 .IR iconv (3)
  35 support.
  36 .PP
  37 Depending on the source and target character set, it may not be possible
  38 to convert all characters to the local character set.  In this case a
  39 substitution character will be used for the characters that cannot be
  40 converted.
  41 .SS
  42 Message Display
  43 The default format used by
  44 .IR scan (1)
  45 will automatically decode MIME-encoded headers.  If you have a custom
  46 .B scan
  47 format, see the examples provided with the
  48 .B nmh
  49 distribution (found in the
  50 .RI \*(lq %nmhetcdir% \*(rq
  51 directory) and
  52 .IR mh\-format (5)
  53 for details on how to make sure your MIME headers are properly decoded.
  54 .PP
  55 By default, if
  56 .B show
  57 detects that it is reading a MIME message it will invoke
  58 .IR mhshow (1).
  59 The default behavior of
  60 .B mhshow
  61 is to only display text parts that are not marked as attachments.  See
  62 .IR mhshow (1)
  63 for details on how to control what
  64 .B mhshow
  65 will display.
  66 .SS
  67 Message Interrogation and Storage
  68 The
  69 .IR mhlist (1)
  70 command will display a listing of the MIME parts contained within a
  71 message.  That information can be used in conjunction with the
  72 .B mhstore
  73 command to save individual parts or content types of a message.  See
  74 .IR mhlist (1)
  75 and
  76 .IR mhstore (1)
  77 for more details on how these commands work.
  78 .SS
  79 Message Composition and Reply
  80 All messages sent by
  81 .IR send (1)
  82 will automatically be processed by
  83 .IR mhbuild (1)
  84 before being passed to
  85 .IR post (1)
  86 for message submission.
  87 .B mhbuild
  88 will use the locale settings to mark text content with the appropriate
  89 character set and apply any necessary encoding.  If you wish to include
  90 text in your message using a character set that does not match your
  91 locale, you will need to specify the character set using an
  92 .B mhbuild
  93 directive; see
  94 .IR mhbuild (1)
  95 for more information.
  96 .PP
  97 For attaching files or composing other non-text content, there are two options:
  98 the attach system and
  99 .B mhbuild
 100 directives.
 101 .PP
 102 The attach system is best suited for content where one or more files are
 103 being attached to a message.  You can use the attach system by either
 104 using the
 105 .B attach
 106 command at the \*(lqWhat now?\*(rq prompt, or by inserting an \*(lqAttach:\*(rq
 107 header in the message draft containing the name of the file you wish to
 108 attach to the message (note that all the
 109 .B attach
 110 command does is place an \*(lqAttach:\*(rq header in the message draft).
 111 .B mhbuild
 112 will then automatically include the specified file(s) in the outgoing
 113 message.  See
 114 .IR send (1)
 115 for details on how
 116 .B mhbuild
 117 determines the proper content type of attached files.
 118 .PP
 119 The other method of composing MIME messages is to use
 120 .B mhbuild
 121 directives.  This allows exact control over the contents and format of
 122 the MIME message, but has a more complicated syntax.
 123 .IR mhbuild (1)
 124 contains details on the directive syntax and examples of directives
 125 for different media types.  It is important to note that when using
 126 .B mhbuild
 127 directives the user must run
 128 .B mhbuild
 129 outside of
 130 .B send
 131 to have it process directives; when being run by
 132 .BR send ,
 133 .B mhbuild
 134 is configured to not process directives so normal user text is not mistaken
 135 for a directive.  When using directives a user typically uses the
 136 .B mime
 137 command at the \*(lqWhat now?\*(rq prompt to process them.
 138 .PP
 139 When replying to messages using
 140 .IR repl (1)
 141 the traditional MH method of including the original text in the reply does
 142 not interoperate with MIME messages.  The
 143 .B \-convertargs
 144 switch to
 145 .IR repl (1)
 146 provides one solution.  Another solution:  the contrib directory
 147 .RI ( %docdir%/contrib )
 148 contains a Perl program called
 149 .B replyfilter
 150 which will decode text parts and present them in an appropriate manner
 151 to be included in a message reply.  See the comments at the top of
 152 .B replyfilter
 153 for instructions on how to configure
 154 .B nmh
 155 to work with it.
 156 .SS
 157 Message Rewrite
 158 The
 159 .IR mhfixmsg (1)
 160 command can apply various transformations to MIME messages, including
 161 decoding of text parts, converting the character set of text parts,
 162 and insertion of text/plain parts to correspond to text parts of other
 163 subtypes.
 164 .B mhfixmsg
 165 can also repair defects in MIME messages, such as mismatched top-level
 166 boundary indicators and invalid Content-Transfer-Encoding values.
 167 .SH "SEE ALSO"
 168 .IR comp (1),
 169 .IR iconv (3),
 170 .IR mh\-format (5),
 171 .IR mhbuild (1),
 172 .IR mhfixmsg (1),
 173 .IR mhparam (1),
 174 .IR nmh (7),
 175 .IR repl (1),
 176 .IR whatnow (1),
 177 .br
 178 .IR %docdir%/contrib/replyfilter ,
 179 .br
 180 .I %docdir%/contrib/replaliases
 181 .SH BUGS
 182 MIME support should be more integrated into all of the
 183 .B nmh
 184 tools than it currently is.