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sendmail.cf(4)
NAME
sendmail.cf - Contains the sendmail configuration file data
SYNOPSIS
/var/adm/sendmail/sendmail.cf
DESCRIPTION
The sendmail.cf file contains configuration information for the sendmail
daemon. For further information on sendmail, see the sendmail(8) reference
page, the sendmail book by O'Reilly & Associates, or the Sendmail
Installation and Operation Guide. The guide is located at the following
URL:
http://uwsg.ucs.indiana.edu/usail/mail/op/op.html
The sendmail.cf configuration file consists of a series of control lines,
each of which begins with a single character that defines how the rest of
the line is used. Lines beginning with a space or a tab are continuation
lines. Blank lines and lines beginning with a # (number sign) are
comments. The control line can be used for the following functions:
· Defining macros and classes for use within the configuration file
· Defining message precedence for mail delivery
· Defining administrative IDs to override the sender's address
· Defining message headings
· Defining the mail daemon to use
· Defining the syntax version used within the configuration file
· Defining rules and rule sets
· Setting options used by the sendmail command
Defining Syntax Version (V Control Line)
To specify the syntax version used by the sendmail.cf configuration file,
use Vn[/vendorcode], where n is an integer specifying the syntax version.
If n is omitted, the original level 0 is assumed. An optional vendor code
can follow the level. The files supplied by DIGITAL use "V2/DIGITAL" to
specify the syntax version. Versions prior to sendmail Version 8 ignore
Vn[/vendorcode].
DIGITAL UNIX provides tools to help you create a reasonable sendmail.cf
file. See the mailconfig.8X and the mailsetup.8 reference pages for further
information.
Defining Rules and Rule Sets (R Control Line and S Control Line)
Most of the sendmail.cf file consists of rules (R Control lines) and rule
sets. A rule set is a group of rules, prefixed by an S control line. For
example, S3 is rule set 3, while S99 is referred to as rule set 99.
While a rule set must start with an S control line, there is no obvious
"end-of-ruleset" marker. All rules following an S control line are
considered to be part of that rule until either a new S control line, or
the end of the file are encountered.
Defining Macros and Classes (D Control Line and C Control Line)
Macros and classes in the sendmail.cf configuration file are interpreted by
the sendmail daemon. A macro is a symbol that represents a value or
string, for example, or an Internet address. A macro is defined by a D
control line in the sendmail.cf file. Macros are not expanded until the
sendmail daemon loads the rule sets when it starts up. The sendmail.cf
file contains system-defined macros and required macros that you must
define.
A class is a symbol that represents a set of one or more words, for
example, or a filename. Classes are used in pattern matching when the
sendmail daemon is parsing addresses. You can create a class using a list
or you can create a class using a file.
The following letters introduce configuration file control lines that
define macros and classes to set up the sendmail daemon:
DMacroValue
Defines a macro and assigns a value to it. If a second
DMacroValue defines the same symbol, the second definition
replaces the first definition. The symbol must be a single
character selected from the ASCII set. Use uppercase letters for
macros and classes that you define. Lowercase letters and
special symbols are macros and classes defined by the daemon.
CClass String
Defines Class to be a class and assigns a word or group of words
(String) to it. If a second CClass String defines the same
symbol, the String from the second definition is added to the
String from the first definition. No words are deleted from the
class definition. Class specifiers may be any of the uppercase
letters from the ASCII character set. Lowercase letters and
special characters are reserved for system use.
F Class FileName [Format]
Defines symbol Class to be a class and assigns a word or group of
words listed in a separate file to the symbol. You can specify
an optional scanf format specifier. Class specifiers may be any
of the uppercase letters from the ASCII character set. Lowercase
letters and special characters are reserved for system use.
To use a macro or class in a control line, put a $ (dollar sign) before its
name. For example, if the name of the macro is x, use $x when using that
macro in a control line. Without the preceding $, the daemon interprets x
as only the letter "x". The format for specifying conditional expressions
is as follows:
$?Macro Text1 $| Text2 $.
In this format, the symbols have the following meaning:
$? If.
Macro The macro being tested.
Text1 The pattern to be used if $x is defined.
$| Else. (This symbol is not required.)
Text2 The pattern to be used if $Macro is not defined.
$. Specifies the end of the conditional expression.
Do not use any of the characters defined as tokens (by the required macro
o) when defining a word in a class. The sendmail daemon may not be able to
read the definition correctly.
Defining Message Precedence (P Control Line)
The sendmail.cf configuration file also contains lines to define mail-queue
precedence for messages that contain a Precedence: field. Normally, you do
not need to change the values in the default sendmail.cf configuration
file.
The name defined and the numerical value assigned are based on the needs of
the network. Higher numbers have higher priority; numbers less than 0
(zero) indicate that error messages will not be returned to the sender of
these messages. The precedence value is 0 (zero) for any precedence name
not defined in this file. For example, the configuration file may contain
the following entries:
Pfirst-class=0
Pspecial-delivery=100
Pbulk=-60
Pjunk=-100
These entries set special-delivery as the highest priority message and junk
as the lowest priority.
Defining Administrative IDs (T Control Line)
Administrative IDs can override the sender address using the -f flag to the
sendmail command. The sendmail.cf configuration file defines these IDs
with the T control line. For example, the configuration file may contain
the following entries:
Troot
Tdaemon
Tuucp
These entries define IDs root, daemon, and uucp as administrative IDs for
the sendmail command. Alternatively, these IDs could have been defined
using only one T control line:
Troot daemon uucp network
Defining Message Headings (H Control Line)
H control lines define the format of Header lines. If the format of a
header line is defined by an H control line, sendmail will reformat the
header according to this format.
The sendmail command allows the user to configure whether a header is
optional or not depending on the mailer (M control lines) selected to
handle this message. If the selected mailer has the MailerFlag defined in
its F= section, then the header is added. For instance, most mailers have
the F=D flag set; this enables the Date: header to be included in the
message.
The format of the H control line is as follows:
H[?MailerFlags?]FieldName: format
In this format, the variable parameters have the following meaning:
MailerFlags
This field is optional. If you supply it, surround it with ?
(question marks). This field contains mailer flags that
determine whether this H line is used. If the mailer being used
requires the information specified by the mailer flag, then this
H control line is included when formatting the heading.
Otherwise, this H control line is ignored.
FieldName This field contains the text that is displayed as the name of the
field in the heading information. The actual text used is a
matter of choice. Some typical field names include From:, To:,
and Rcvd From:.
format This field defines the information that is displayed following
the field name. It usually uses a sendmail macro to specify the
information.
The sendmail command does not do any special processing for the header
mailer flags; their use is purely by convention. See the section on
Specifying Mailer Flags for more detail.
The following is a list of parts that the sendmail daemon expects mail to
have. Note that these parts must appear in the same order as listed here.
1. An operating system From line (defined by the five characters: F, r,
o, m, and space)
2. Mail header lines that begin with a keyword followed by a colon, such
as From: or To:
3. An empty line
4. The body of the message
The sendmail daemon detects the operating system From line by checking the
first five characters of the first line. After that, header lines are
processed. When it detects a line that does not begin with a keyword
followed by a colon, it ends header line processing. If an empty line
occurs at that point, it is ignored.
Mailer flags or the mailer itself determine if an operating system From:
line is generated. Other header lines are present (or not) depending on
those defined in the sendmail configuration file, those specified by mailer
flags, and those present in incoming mail.
Note that the binmail daemon generates a From: line on all local
deliveries. The sendmail mailer flags do not allow you to alter this.
The following example lines are from a typical sendmail.cf file:
H?P?Return-Path: <$g>
This line defines a field called Return-Path: that displays the contents of
the $g macro (sender address relative to the receiver). The ?P? portion
indicates that this line is only used if the mailer uses the P flag (the
mailer requires a Return-Path line).
HReceived: $?sfrom $s $.by $j ($v/$Z)
id $i; $b
This line defines a field called Received. This field displays the
following information:
$?sfrom $s $.
If an s macro is defined (sender's hostname), displays the text
from followed by the content of the $s macro.
by $j Displays the text by followed by the content of the $j macro
(official name for this site).
($v/$Z) Displays the version of the sendmail daemon ($v) and the version
of the sendmail.cf file ($Z) set off by parentheses and separated
by a slash.
id $i; Displays the text id followed by the content of the $i macro
(mail-queue ID of the message) and a ; (semicolon).
$b Displays the current date.
Defining a Mailer (M Control Line)
A mailer is a daemon that delivers mail either locally or over some type of
network to another system. Use control lines that begin with the letter M
to define the characteristics of a mailer daemon that interfaces with
sendmail.
Note that defining a mail daemon entry (mailer) in the sendmail.cf
configuration file does not ensure that it will be used. You must also
define rewrite rules to ensure the address format resolves to that mailer.
The format of a mailer definition control line is as follows:
M=MailerName,
P=Path,
F=Flags,
S=Integers,E=EndOfLine,
A=String,
M=Limit
The following paragraphs and examples describe the parameters for the
mailer definition.
Specifying a Mailer Name (MMailerName)
Each mailer must have an internal name. The name can be any string that
you choose, except that the names local and prog are reserved for the
mailers for local delivery and delivery to daemons. You must provide
definitions for these two mailers in the sendmail.cf configuration file if
they are not already there (the default configuration file contains these
definitions). To define the mailer name, put the name immediately after the
M in the mailer-definition control line:
MMailerName
For example, the following segment introduces the definition line for a
mailer called lan:
Mlan
Defining the Path to the Mailer Daemon (P=Path)
Specify the location of the mailer daemon with the P field in the mailer
definition. This field has the format:
P=Path
The Path defines the full pathname of the mailer daemon on the local
system. If the mailer daemon is the sendmail daemon version of Simple Mail
Transfer Protocol (SMTP) (daemon), use the string [IPC] as the path. For
example, the following two mailer-definition fragments define a local
mailer at /usr/bin/mail and another mailer that is the sendmail daemon
implementation of SMTP:
Mlocal, P=/usr/bin/mail,
Mlan, P=[IPC],
Specifying Mailer Flags (F=Flags)
Mailer flags provide further information to the sendmail daemon about the
mailer daemon being described. Specify mailer flags with the F field in the
mailer-definition. This field has the format:
F=Flags
This field defines the meaning for the flags that the sendmail daemon
recognizes. For example, the following mailer-definition fragment uses the
-rlsm flags to indicate that the mailer requires a -r flag, delivers
locally, needs quotation marks stripped from addresses, and can deliver to
more than one user at a time:
Mlocal, P=/usr/bin/mail, F=rlsm,
Flags available for the F=Flags field are as follows:
C If this flag is set, this mailer inspects the address of any
incoming mail that it processes for the presence of an @ (at
sign). If it finds an @, it saves the @ and the remainder of the
address to be used when rewriting addresses in header lines in
the message (when mail is forwarded to any mailer).
The receiving mailer adds the saved portion of the address to any
address that does not contain an @, after the address has been
processed by rule set 3 (this processing does not depend upon a
mailer flag; it always occurs). Do not use this flag for general
operation, since it does not interpret complex, route-based
addresses properly.
D The mailer defined in this mailer-definition control line needs a
Date: or Resent-Date: header line.
e The mailer defined in this mailer-definition control line is
expensive to connect to. If the C configuration option is set,
mail for this mailer is always placed in the queue.
E This flag causes the mailer in the definition control line to
allow lines beginning with the exact six characters >, F, r, o,
m, and space to appear in the text of a message. Normally From:
lines are treated as header lines. The E flag allows operating
system From: lines (or any other text lines beginning with those
six characters) to appear in the body of the message without
being interpreted as the start of a new message.
f The mailer in the mailer-definition control line needs a -f flag.
The flag is inserted into the call for the mailer followed by the
expansion of the $g macro (sender's address relative to the
receiver).
F The mailer in the mailer-definition control line needs a From: or
Resent-From: header line. This header is optional depending on
the mailer (M control lines) selected to handle this message.
h Preserves uppercase letters in hostnames for the mailer in the
mailer-definition control line.
I The mailer in the mailer-definition control line uses Simple Mail
Transfer Protocol (SMTP) to communicate with another SMTP server
that is part of the sendmail daemon. When communicating with
another sendmail daemon, the mailer can use features that are not
part of the standard SMTP protocol. This option is not required,
but causes the transmission to operate more efficiently than
without the option.
l The mailer in the mailer-definition control line is local; final
delivery will be performed.
L The L flag enforces SMTP line lengths.
m The mailer in the mailer-definition control line can be sent to
multiple users on the same host in one transaction. The $u macro
contains the recipient's username. When a $u macro occurs in the
String part of the mailer-definition, (for example A=mail -r $g
-d $u) and the m flag is set, $u is expanded to become a list of
all the recipients.
M The mailer in the mailer-definition control line needs a
Message-Id header. This header is optional depending on the
mailer (M control lines) selected to handle this message.
P The mailer in the mailer-definition control line needs a Return-
Path: header line. This header is optional depending on the
mailer (M control lines) selected to handle this message.
x The mailer in the mailer-definition control line needs a Full-
name: header. This header is optional depending on the mailer (M
control lines) selected to handle this message. For versions
prior to Version 8, this flag also enables the MULT option
required by the mail11v3 program to handle multiple recipients.
Define Sender Rewriting Rules (S=Envelope/Header)
Define Recipient Rewriting Rules (R=Envelope/Header)
After a mailer has been selected by the S0 ruleset, sendmail performs
additional processing on the addresses. Sender addresses are processed by
the rule(s) specified by the S= section, while recipient addresses are
processed by the rule(s) specified by the R= section.
The sendmail program allows you to specify either a single rule (for
example, S=14), or split rewriting rules. (For example, S=14/24). If split
rules are specified, envelope addresses are processed by the first rule
(for example, 14), while header addresses are processed by the later rule
(for example, 24).
Configuration File Revision Level Option (DZNumber)
The configuration file revision level macro, Z, helps you track changes
that you make to the sendmail configuration file. Each time that you make
a change to the sendmail configuration file, you should also change the
value of this macro. Choose any format for the number that you define.
For example, if the sendmail configuration file is at level 3.1, the
following entry appears in the sendmail configuration file:
DZ3.1
A text string can also be used for this macro:
DZversion_one
RELATED INFORMATION
Commands: mailconfig(8X), mailsetup(8), mail_manual_setup(7),
sendmail.m4(8), sendmail(8)