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 stan-
dard default MH mail header:
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 MH@UCI-ICSA.ARPA. 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:
Date: Added by post, contains the date and time of the message's entry
into the transport system.
From: 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.
Sender: 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.
To: Contains addresses of primary recipients.
cc: Contains addresses of secondary recipients.
Bcc: 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
Fcc: Causes post to copy the message into the specified folder for
the sender, if the message was successfully given to the tran-
A unique message identifier added by post, if the -msgid flag is
Subject: 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.
Resent-To: New recipients for a message resent by dist.
Resent-cc: 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
A unique identifier of a message resent by dist. This is
appended by post if the -msgid flag is set.
Resent: Annotation added by dist when the -annotate flag is specified.
Forwarded: Annotation added by forw when the -annotate flag is specified.
Replied: 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 mes-
sages is enabled and requested. For more information on codeset
conversion, see the section on internationalization features in
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 interna-
tionalization features in mh(1).
Standard location of mail drop
Standard for the Format of ARPA Internet Text Messages (RFC 822)