mh-mail
Purpose
The message format for the Message Handling (MH) Package.
Description
The Message Handling (MH) Package processes messages in a
particular format. While this format is different from
that used by the Bell and Berkeley mail systems, the MH
package can read Bell and Berkeley message files.
Each user has a mail drop that initially receives all
messages processed by the post or spost command. The inc
command reads from that mail drop and incorporates the
new messages found there into the user's own mail folder
(typically inbox). The mail drop consists of one or more
messages.
Messages are expected to consist of lines of text.
Graphics and binary data are not handled. No data com-
pression is accepted. All text is ASCII 7-bit data.
The general memo framework of the ARPA Internet RFC 822
standard 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 header, and the free-
format portion is called the body. The header must
always exist, but the body is optional. These parts are
separated by an empty line, that is, two consecutive
newline characters. Within messages, the header and body
may be separated by a line consisting of dashes:
To:
cc:
Subject
-------
The header is composed of one or more header components.
Each header component can be viewed as a single logical
line of ASCII characters. If the text of a header compo-
nent extends across several lines, the continuation lines
are indicated by leading spaces or tab characters.
Each header component is composed of a keyword or name,
along with associated text. The keyword begins at the
left margin, may not contain space or tab characters, may
not exceed 63 characters, and ends with a : (colon).
Certain components (as identified by their keywords) must
follow rigidly the defined formats in their text
portions.
The text for most formatted components (for example,
Date: and Message-Id:) is produced automatically. The
text for other components must be entered by the user
(for example, To: and cc:). Multiple addresses are sepa-
rated by commas. A missing host/domain is assumed to be
the local host domain.
Header Components
Date: Added by post, spost, or the mail
transport system; contains the date
and time of the message's entry into
the transport system.
From: Added by post or spost; contains the
address of the author or authors (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 both are present).
Sender: Added by post or spost 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 recipi-
ents.
cc: Contains addresses of secondary
recipients
Bcc: Contains still more recipients.
However, the Bcc: line is not copied
into the message as delivered, so
these recipients are not listed. The
MH package uses an encapsulation
method for blind copies.
Fcc: Causes the post or spost command to
copy the message into the specified
folder for the sender, if the message
was successfully given to the trans-
port system.
Message-Id: A unique message identifier added by
post or spost if the -msgid flag is
set.
Subject: Sender's commentary. It is displayed
by the scan command.
In-Reply-To: A commentary line added by the repl
command when replying to a message.
Resent-Date: Added when redistributing a message
by post or spost.
Resent-From: Added when redistributing a message
by post or spost.
Resent-To: New recipients for a message resent
by the dist command.
Resent-cc: More recipients. See cc: and
Resent-To:.
Resent-Bcc: More recipients. See Bcc: and
Resent-To:.
Resent-Fcc: Copies resent message into a folder.
See Fcc: and Resent-To:.
Resent-Message-Id: A unique identifier attached by post
or spost if you specify the -msgid
flag. See Message-Id: and
Resent-To:.
Resent: Annotation that dist uses when you
specify the -annotate flag.
Forwarded: Annotation that the forw command uses
when you specify the -annotate flag.
Replied: Annotation that repl uses when you
specify the -annotate flag.
Files
/usr/mail/$USER Location of mail drop
Related Information
Standard for the Format of ARPA Internet Text Messages,
RFC 822.
The "Overview of the Message Handling Package" in Man-
aging the AIX Operating System.