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   1 .TH MH\-MIME %manext7% "September 25, 2016" "%nmhversion%"
   2 .\"
   3 .\" %nmhwarning%
   4 .\"
   5 .SH NAME
   6 mh\-mime \- Overview of
   7 .IR nmh (7)
   8 MIME message composition and display
   9 .\"
  10 .SH DESCRIPTION
  11 The acronym MIME stands for Multipurpose Internet Mail Extensions, the
  12 format of Internet messages used to send multi\-media content.
  13 The
  14 .B nmh
  15 command suite has support for the display and composition of MIME messages, but
  16 currently MIME support is not completely integrated into all tools.  This
  17 document provides an overview as to which tools support MIME message display,
  18 storage, and composition.
  19 .SS
  20 Local Character Set Conversion
  21 All of the
  22 .B nmh
  23 commands convert non\-native character sets to the local character set,
  24 as specified by the operating system locale settings.  See
  25 .IR locale (1)
  26 for more details on the environment variables used to set the
  27 local character set.  Character set conversion will only take place if
  28 .B nmh
  29 was built with
  30 .IR iconv (3)
  31 support.  See the
  32 .IR mhparam (1)
  33 man page for how determine whether your
  34 .B nmh
  35 installation includes
  36 .IR iconv (3)
  37 support.
  38 .PP
  39 Depending on the source and target character set, it may not be possible
  40 to convert all characters to the local character set.  In this case a
  41 substitution character will be used for the characters that cannot be
  42 converted.
  43 .SS
  44 Message Display
  45 The default format used by
  46 .IR scan (1)
  47 will automatically decode MIME-encoded headers.  If you have a custom
  48 .B scan
  49 format, see the examples provided with the
  50 .B nmh
  51 distribution (found in the
  52 .RI \*(lq %nmhetcdir% \*(rq
  53 directory) and
  54 .IR mh\-format (5)
  55 for details on how to make sure your MIME headers are properly
  56 decoded.
  57 .PP
  58 By default, if
  59 .B show
  60 detects that it is reading a MIME message it will invoke
  61 .IR mhshow (1).
  62 The default behavior of
  63 .B mhshow
  64 is to only display text parts that are not marked as attachments.  See
  65 .IR mhshow (1)
  66 for details on how to control what
  67 .B mhshow
  68 will display.
  69 .SS
  70 Message Interrogation and Storage
  71 The
  72 .IR mhlist (1)
  73 command will display a listing of the MIME parts contained within a
  74 message.  That information can be used in conjunction with the
  75 .B mhstore
  76 command to save individual parts or content types of a message.  See
  77 .IR mhlist (1)
  78 and
  79 .IR mhstore (1)
  80 for more details on how these commands work.
  81 .SS
  82 Message Composition and Reply
  83 All messages sent by
  84 .IR send (1)
  85 will automatically be processed by
  86 .IR mhbuild (1)
  87 before being passed to
  88 .IR post (1)
  89 for message submission.
  90 .B Mhbuild
  91 will use the locale settings to mark text content with the appropriate
  92 character set and apply any necessary encoding.  If you wish to include
  93 text in your message using a character set that does not match your
  94 locale, you will need to specify the character set using a
  95 .B mhbuild
  96 directive; see
  97 .IR mhbuild (1)
  98 for more information.
  99 .PP
 100 For attaching files or composing other non-text content, there are two options: the attach system and
 101 .B mhbuild
 102 directives.
 103 .PP
 104 The attach system is best suited for content where one or more files are
 105 being attached to a message.  You can use the attach system by either
 106 using the
 107 .B attach
 108 command at the \*(lqWhat now?\*(rq prompt, or by inserting an \*(lqAttach:\*(rq
 109 header in the message draft containing the name of the file you wish to
 110 attach to the message (it should be noted all that the
 111 .B attach
 112 command does is place an \*(lqAttach\*(rq header in the message draft).
 113 .B Mhbuild
 114 will then automatically include the specified file(s) in the outgoing
 115 message.  See
 116 .IR send (1)
 117 for details on how
 118 .B mhbuild
 119 determines the proper content type of attached files.
 120 .PP
 121 The other method of composing MIME messages is to use
 122 .B mhbuild
 123 directives.  This allows exact control over the contents and format of
 124 the MIME message, but has a more complicated syntax.
 125 .IR mhbuild (1)
 126 contains details on the directive syntax and examples of directives
 127 for different media types.  It is important to note that when using
 128 .B mhbuild
 129 directives the user must run
 130 .B mhbuild
 131 outside of
 132 .B send
 133 to have it process directives; when being run by
 134 .BR send ,
 135 .B mhbuild
 136 is configured to not process directives so normal user text is not mistaken
 137 for a directive.  When using directives a user typically uses the
 138 .B mime
 139 command at the \*(lqWhat now?\*(rq prompt to process them.
 140 .PP
 141 When replying to messages using
 142 .IR repl (1)
 143 the traditional MH method of including the original text in the reply does
 144 not interoperate with MIME messages.  The
 145 .B \-convertargs
 146 switch to
 147 .IR repl (1)
 148 provides one solution.  Another solution:  the contrib directory
 149 .RI ( %docdir%/contrib )
 150 contains a Perl program called
 151 .B replyfilter
 152 which will decode text parts and present them in an appropriate manner
 153 to be included in a message reply.  See the comments at the top of
 154 .B replyfilter
 155 for instructions on how to configure
 156 .B nmh
 157 to work with it.
 158 .SS
 159 Message Rewrite
 160 The
 161 .IR mhfixmsg (1)
 162 command can apply various transformations to MIME messages, including
 163 decoding of text parts, converting the character set of text parts,
 164 and insertion of text/plain parts to correspond to text parts of other
 165 subtypes.
 166 .B mhfixmsg
 167 can also repair defects in MIME messages, such as mismatched top-level
 168 boundary indicators and invalid Content-Transfer-Encoding values.
 169 .SH "SEE ALSO"
 170 .IR comp (1),
 171 .IR iconv (3),
 172 .IR mh\-format (5)
 173 .IR mhbuild (1),
 174 .IR mhfixmsg (1),
 175 .IR mhparam (1),
 176 .IR nmh (7),
 177 .IR repl (1),
 178 .IR whatnow (1),
 179 .br
 180 .IR %docdir%/contrib/replyfilter ,
 181 .br
 182 .I %docdir%/contrib/replaliases
 183 .SH BUGS
 184 MIME support should be more integrated into all of the
 185 .B nmh
 186 tools than it currently is.