+that is present in the message, such as comments in the
+\*(lqContent-Type\*(rq header.
+.PP
+If the
+.B \-disposition
+switch is present, then the listing will show any relevant information from
+the \*(lqContent-Disposition\*(rq header.
+.SS "Simplified Attachment Interface"
+For users who wish to simply attach files to text content,
+.B mhbuild
+will scan the composition file for \*(lqAttach\*(rq headers.
+An
+\*(lqAttach\*(rq header contains a filename that will be appended to the
+message using normal MIME encapsulation rules.
+One filename is allowed
+per \*(lqAttach\*(rq header, but multiple \*(lqAttach\*(rq headers are
+allowed per composition file.
+.PP
+These files will be appended after any other MIME content, including any
+content specified by
+.B mhbuild
+directives (see below).
+See
+.IR send (1)
+for more details.
+.PP
+By default, the Content-Disposition will be \*(lqattachment\*(rq.
+.B mhbuild
+looks for user profile and
+.I mhn.defaults
+entries of the form
+.PP
+.RS 5
+.BI mhbuild-disposition- type / subtype
+.RE
+or
+.RS 5
+.BI mhbuild-disposition- type
+.RE
+.PP
+to supply the disposition value.
+The only supported values are
+\*(lqattachment\*(rq
+and
+\*(lqinline\*(rq.
+.SS "Convert Interface"
+The convert interface is a powerful mechanism that supports
+replying to MIME messages.
+These placeholders are used in the following
+description:
+.RS 5
+.TP 15
+.PD 0
+TYPE
+content type/subtype
+.TP
+CONVERTER
+external program, and any fixed arguments, to convert content, such as
+from a request to a reply
+.TP
+ARGSTRING
+arguments to pass from
+.B repl
+to
+.I CONVERTER
+.TP
+FILE
+full path of message being replied to
+.PD
+.RE
+.PP
+.RE
+The convert support is based on pseudoheaders of the form
+.PP
+.RS 5
+.nf
+.BI Nmh-mhbuild-file- TYPE : \0FILE
+.BI Nmh-mhbuild-args- TYPE : \0ARGSTRING
+.fi
+.RE
+.PP
+in the draft.
+For each such pseudoheader, mhbuild looks in the
+profile and
+.I mhn.defaults
+for this corresponding
+.I TYPE
+entry to find the
+converter that supports it:
+.PP
+.RS 5
+.BI mhbuild-convert- TYPE : \0CONVERTER
+.RE
+.PP
+It's a fatal error if no such entry is found for
+.IR TYPE .
+An empty
+entry, e.g.,
+.PP
+.RS 5
+.B mhbuild-convert-text/html:
+.RE
+.PP
+excludes parts of that
+.I TYPE
+from the draft.
+.PP
+The
+.I mhn.defaults
+file
+contains default
+.B mhbuild-convert-text/html
+and
+.BR mhbuild-convert-text/plain
+entries.
+Profile entries can be used to override corresponding
+.I mhn.defaults
+entries, as usual. Text converters should limit text line lengths
+to a maximum of 78 characters, and must limit them to a maximum of 998
+characters, per RFC 5322 Sec.\& 2.1.1.
+.PP
+For each
+.I TYPE
+part in
+.IR FILE ,
+.B mhbuild
+runs
+.I CONVERTER ARGSTRING
+on the content of the part.
+Each part in
+.I FILE
+that has no corresponding TYPE entry in the profile or
+.I mhn.defaults
+is
+excluded from the draft; the user can include them using mhbuild
+directives.
+.PP
+.B repl
+inserts
+.B Nmh-mhbuild-text/html:
+and
+.B Nmh-mhbuild-text/plain:
+pseudoheaders in every draft.
+The user can prevent insertion of
+content parts of either of those types by putting corresponding empty
+entries in their profile.
+.PP
+Only the highest precedence alternative with a supported
+.I TYPE
+of a multipart/alternative part is used.
+.PP
+mhn.defaults.sh selects the text/html-to-text/plain converter at
+install time.
+It includes
+.B iconv
+and
+.BR par ,
+or
+.BR fmt ,
+in the pipeline only if they are found.
+.PP
+Some content types require the addition of parameters to the
+Content-Type header, such as
+\*(lqmethod=REPLY\*(rq
+for text/calendar.
+.B mhbuild
+looks for a Content-Type header, followed
+by a blank line, at the beginning of the converter output.
+If one is
+found, it is used for the corresponding part in the reply draft.
+.PP
+The convert interface doesn't support different
+.IR ARGSTRING s
+or different converters for different parts of the same
+.IR TYPE .
+That would require associating parts by part number with the
+.IR ARGSTRING s
+or converters.
+Instead, that can be done (currently, without using
+the convert support), with
+.B mhbuild
+directives as described below, e.g.,
+.PP
+.RS 5
+#text/html; charset=utf-8 *8bit | mhstore -noverbose -part 42.7 -outfile - | w3m -dump -cols 64 -T text/html -O utf-8
+.RE
+.PP
+The only way to mix
+convert
+pseudoheaders and
+.B mhbuild
+directives is to insert the directives before
+.B mhbuild
+is run, which is typically done by entering
+.I mime
+at the \*(lqWhat now?\*(rq prompt, or with an
+.B \-editor mhbuild
+switch.
+.PP
+These (optional) setup steps can make the convert support
+easier to use:
+.TP 5
+1)
+If the
+.B par
+program is installed on your system, it will be set by default
+(in
+.IR mhn.defaults )
+to filter the converter output.
+It helps to
+set the
+PARINIT
+environment variable, as described in its man page.
+.TP 5
+2)
+Add this line to your profile:
+.IP "" 10
+mhbuild-next: $EDITOR
+.IP "" 5
+assuming that your EDTIOR environment variable is set; if not, replace
+EDITOR with the name of your editor.
+Without that profile entry, a
+response of \*(lqe[dit]\*(rq at the What now? prompt will require
+specification of your editor if an
+.B \-editor mhbuild
+switch is used.
+.RE
+.TP 5
+3)
+If using
+.BR repl ,
+source the Bourne-shell compatible functions in
+.IR %docdir%/contrib/replaliases .
+.br
+That script also sets the
+PARINIT
+environment variable if it was not set.
+.RE
+.SS "Translating the Composition File"
+.B mhbuild
+is essentially a filter to aid in the composition of MIME
+messages.
+.B mhbuild
+will convert an
+.B mhbuild
+\*(lqcomposition file\*(rq
+into a valid MIME message.
+A
+.B mhbuild
+\*(lqcomposition file\*(rq
projects / nmh / blobdiff