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sendmail.cf(4) Kernel Interfaces Manual 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 send- mail 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 # (num- ber 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 administra- tive 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 inter- preted by the sendmail daemon. A macro is a symbol that represents a value or string, for example, or an Internet address. A macro is de- fined by a D control line in the sendmail.cf file. Macros are not ex- panded 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 ex- ample, 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: 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 up- percase letters for macros and classes that you define. Lowercase let- ters and special symbols are macros and classes defined by the daemon. 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. 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 op- tional scanf format specifier. Class specifiers may be any of the up- percase 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 us- ing that macro in a control line. Without the preceding $, the daemon interprets x as only the letter "x". The format for specifying condi- tional expressions is as follows: $?Macro Text1 $| Text2 $. In this format, the symbols have the following meaning: If. The macro being tested. The pattern to be used if $x is defined. Else. (This symbol is not required.) The pattern to be used if $Macro is not de- fined. 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. Nor- mally, 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 configura- tion 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 de- fined 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 mail- ers 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?]Field- Name: format In this format, the variable parameters have the following meaning: 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 speci- fied by the mailer flag, then this H control line is included when for- matting the heading. Otherwise, this H control line is ignored. 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:. 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. An operating system From line (defined by the five characters: F, r, o, m, and space) Mail header lines that begin with a keyword fol- lowed by a colon, such as From: or To: An empty line 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 key- word 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) de- pending 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 deliv- eries. 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 con- tents 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: If an s macro is defined (sender's hostname), displays the text from followed by the content of the $s macro. Dis- plays the text by followed by the content of the $j macro (official name for this site). Displays the version of the sendmail daemon ($v) and the version of the sendmail.cf file ($Z) set off by parentheses and separated by a slash. Displays the text id followed by the content of the $i macro (mail-queue ID of the message) and a ; (semicolon). Dis- plays 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 in- terfaces with sendmail. Note that defining a mail daemon entry (mailer) in the sendmail.cf con- figuration 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=Mailer- Name, 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 pro- vide definitions for these two mailers in the sendmail.cf configuration file if they are not already there (the default configuration file con- tains these definitions). To define the mailer name, put the name imme- diately 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 de- fine 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, deliv- ers locally, needs quotation marks stripped from addresses, and can de- liver 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: 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. The mailer defined in this mailer-de- finition control line needs a Date: or Resent-Date: header line. The mailer defined in this mailer-definition control line is ex- pensive to connect to. If the C configuration option is set, mail for this mailer is always placed in the queue. 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. The mailer in the mailer-definition control line needs a -f flag. The flag is in- serted into the call for the mailer followed by the expansion of the $g macro (sender's address relative to the receiver). 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. Preserves uppercase letters in hostnames for the mailer in the mailer-definition control line. The mailer in the mailer-defin- ition control line uses Simple Mail Transfer Protocol (SMTP) to communicate with another SMTP server that is part of the send- mail 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 op- tion. The mailer in the mailer-definition control line is lo- cal; final delivery will be performed. The L flag enforces SMTP line lengths. The mailer in the mailer-definition control line can be sent to multiple users on the same host in one transac- tion. 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 ex- panded to become a list of all the recipients. 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. 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. The mailer in the mailer-definition control line needs a Full-name: header. This header is optional depending on the mailer (M control lines) se- lected 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), send- mail.m4(8), sendmail(8) delim off sendmail.cf(4)