mh-mail - Message format for the MH message system
MH processes messages in a particular format. Although
neither Bell nor Berkeley mailers produce message files in
the format that MH prefers, MH can read message files in
that format.
Each user has a maildrop that initially receives all messages
processed by the post command (see post(8)).
The inc command reads from the maildrop and incorporates
the new messages found there into the user's own +inbox
folder. The maildrop consists of one or more messages.
Messages are expected to consist of lines of text. Graphics
and binary data are not handled. No data compression
is accepted. All text is in ASCII 7-bit data.
The general memo framework of RFC 822 is used. A message
consists of a block of information in a rigid format, followed
by general text with no specified format. The
rigidly-formatted first part of a message is called the
message header; the free-format portion is called the
body. The header must always exist, but the body is
optional. These parts are separated by a blank line or by
a line of dashes. The following example shows the standard
default MH mail header:
To: cc: Subject: --------
The header is composed of one or more header items. Each
header item can be viewed as a single logical line of
ASCII characters. If the text of a header item extends
across several real lines, the continuation lines are
indicated by leading spaces or tabs.
Each header item is called a component and is composed of
a keyword or name, along with associated text. The keyword
begins at the left margin, and is terminated by a
colon (:). It cannot contain spaces or tabs, and cannot
exceed 63 characters, as specified by RFC 822.
The text for most formatted components, such as Date: and
Message-Id:, is produced automatically. The user enters
address fields such as To: and cc:, and the Subject:
field. Internet addresses are assigned mailbox names and
host computer specifications. The general format is
local@domain, for example, MH@UCI or [email protected]. A
comma (,) separates multiple addresses. A missing
host/domain is assumed to be the local host/domain.
A blank line (or a line of dashes) signals that all following
text up to the end of the file is the body of the
message. No formatting is expected or enforced within the
body.
The following is a list of header components that are considered
meaningful to MH programs: Added by post, contains
the date and time of the message's entry into the transport
system. Added by post, contains the address of the
author or authors (there may be more than one if a Sender:
field is present). Replies are typically directed to
addresses in the Reply-To: or From: field. The former has
precedence, if present. Added by post in the event that
the message already has a From: line. This line contains
the address of the actual sender. Replies are never sent
to addresses in the Sender: field. Contains addresses of
primary recipients. Contains addresses of secondary
recipients. Contains the addresses of recipients who
receive blind carbon copies of the message. The Bcc: line
does not appear on the message as sent, so these recipients
are not listed. Recipients in the Bcc: field receive
a copy of the message with a minimal header. MH uses an
encapsulation method for blind copies; see send(1).
Causes post to copy the message into the specified folder
for the sender, if the message was successfully given to
the transport system. A unique message identifier added
by post, if the -msgid flag is set. Sender's commentary.
It is displayed by scan. A commentary line added by repl
when replying to a message. Added by post when a message
is redistributed. Added by post when a message is redistributed.
New recipients for a message resent by dist.
New secondary recipients for a message resent by dist.
New blind carbon copy recipients for a message resent by
dist. Places a copy of a message resent by dist into the
sender's folder. A unique identifier of a message resent
by dist. This is appended by post if the -msgid flag is
set. Annotation added by dist when the -annotate flag is
specified. Annotation added by forw when the -annotate
flag is specified. Annotation added by repl when the
-annotate flag is specified. Specifies the MIME version
number. This header entry is used or added by MH software
only when codeset conversion of mail messages is enabled
and requested. For more information on codeset conversion,
see the section on internationalization features in
mh(1). Specifies the content type, which is always
TEXT/PLAIN, plus a charset value that names a coded character
set (codeset). This header entry is used or added
by MH software only when codeset conversion of mail messages
is enabled and requested. For more information on
codeset conversion, see the section on internationalization
features in mh(1).
Standard location of mail drop
Standard for the Format of ARPA Internet Text Messages
(RFC 822) delim off
mh-mail(4)
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