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config -- System Administration
File that configures smail
/usr/lib/mail/config
File /usr/lib/mail/config holds instructions that configure the mailer-
delivery program smail. You can modify this file to supplement, modify, or
override smail's default configuration.
Please note that this file is in no way related to file
/usr/lib/uucp/config, which can be used to configure the Taylor UUCP
system. For details on how to configure UUCP, see the Lexicon entry for
/usr/lib/mail/config, which immediately follows this article in the
Lexicon.
The rest of this article describes config, the attributes you can set
within it, and how the setting of each attribute affects smail's behavior.
Suite of Configuration Files
To begin, your machine can have two smail configuration files: a primary
one, and a secondary one. Either can reset the values of any smail
variable; for example, each can define names for the local host, define
where files reside, or set the values for site-definable message-header
fields. You are not obliged to use a configuration file: if smail's
default configuration suits you, then you can rename or move the primary
configuration file so it will no longer be read. Likewise, if you have a
primary configuration file, you are not obliged to have a secondary one.
smail reads the primary configuration file first, then the secondary
configuration file. The values in the secondary configuration file can
override those set in the primary file; the primary file, in turn, can
redefine the name of the secondary configuration file. This gives you
great flexibility to configure smail to suit your needs and preferences.
Format of a Configuration File
A configuration file consists of instructions; each instruction, in turn,
sets an attribute to a value. Attributes come in three flavors: string,
numeric, and Boolean. To set a variable to a string or numeric value, use
the form:
variable = value
For example, the instructions
postmaster = tron@glotz.uucp
domains = wall.com
spool_mode = 0664
set the default address for the postmaster to tron@glotz.uucp, the
attribute domains to wall.com, and the permissions for spool files to
permit the file's owner and group to write into it.
Boolean attributes are either turned off or turned on. To turn on a
Boolean attribute, use the notation:
+boolean-attribute
To turn it off, use the notation:
-boolean-attribute
You can also use the notation -attribute to set a numeric variable to zero
and to un-set a value for a string variable. For example, the following
instructions disable the use of an external transport file and tells smail
that configuration files are not optional:
-transport_file
+require_configs
smail ignores blanks lines within a configuration file. If smail
encounters a `#' character, it ignores that character plus all text to its
right; thus, you can use this character to introduce a comment.
If a line begins with white space, smail assumes that it continues the
previous line; in this way, you can extend an instruction over more than
one line. For example, the following instructions set the Received: header
field to use for messages to a multi-line value, and also set the name of a
user that has few access capabilities:
# Use a verbose format for the Received: header field
received_field = "Received: by $primary_name
with smail ($version_string)
id <$message_id@$primary_name); $date"
nobody = unknown # comment: user "unknown" has few access capabilities
smail Attributes
The following names the attributes that you can set in a configuration
file. Each attribute's name is followed by its type and its default
setting in parentheses.
auth_domains (string, off)
Name the domains for which your host is considered authoritative --
i.e., the domains that your host knows how to access directly. The
domain names must be separated by a single colon character `:'. Mail
addressed to any domain named in this list will not be forwarded to
the smart host (described below).
auto_mkdir (Boolean, on)
If set, smail creates all directories required for spooling and
logging if they do not exist. However, smail will never create
required parent directories.
auto_mkdir_mode (integer, 0755)
When smail creates a directory, give it this permission mask. For
details on what the numbers in a permission mask mean, see the Lexicon
entry for chmod.
console (string, /dev/console)
Name the console device. This device is used as a last resort in
attempting to write panic messages.
copying_file (string, COPYING)
The path name to file COPYING, which states your distribution rights
and details the warranty information from the authors of smail. If
this does not begin with `/', smail assumes that it is in the
directory named by attribute smail_lib_dir (described below).
date_field (string, Date: $spool_date)
smail expands this string to form field Date: in a mail message's
header, should the header not already contain such a field.
delivery_mode (string, foreground)
The default mode for delivering new mail. This can be one of the
following values:
foreground
Immediate delivery via the process that received the message.
background
Immediate delivery via a child process. The process that
received the message exits immediately.
queued
Do not attempt delivery until a later queue run.
director_file (string, directors)
This names the file that configures smail's directors. If this does
not begin with `/', smail assumes that it is in the directory named by
variable smail_lib_dir (described below).
domains (string)
This sets the domain name that smail writes into the header of an
outgoing mail message. It is computed at run time. If attribute
visible_name is turned off, then smail sets it to the first name set
by attribute hostnames. If hostnames is not set, then smail constructs
the domain-name host names of the form hostname.domain. hostname is
set in file /etc/uucpname domain is a name set by the attribute
domains-- smail uses each entry in domains, in order, to create the
hostnames value.
For sites in the UUCP zone, domains often will merely be set to the
string uucp. Finally, you can use the variable $visible_name within
the string to which you set this attribute.
For compatibility with earlier versions of smail, this attribute can
also be called visible_domains.
error_copy_postmaster (Boolean, off)
Send the postmaster a copy of every error message. Normally, smail
sends the postmaster only the errors that appear to result from
administrator mistakes. If you set this attribute, then smail also
sends the postmaster the errors that are returned to the sender or
that are mailed to owners of mailing lists.
fnlock_interval (number, 3)
Set the sleep interval between retries while attempting to lock
mailbox files with a lockfile-based locking protocol. Under COHERENT,
the function sleep() has a one-second granularity; therefore, you must
this value to at least two.
fnlock_mode (number, 0666)
Create mailbox lock files.
fnlock_retries (number, five)
The number of times smail attempts to lock mailbox files using a file-
based locking protocol.
from_field (string)
smail expands this string to form the fields From: and Sender: in a
mail message's header. The expanded string must begin with From:,
which may be replaced by other strings to form an actual header field.
The default value is:
From: $sender${if def:sender_name: ($sender_name)}
grades (string)
Set the grade (or priority) characters that correspond to values of
the Precedence: field in a mail message's header. The fields within
the string are separated by `:'; precedence strings alternate with
grade characters. Numbers have higher priority than upper-case
letters, which in turn are higher than lower-case letters. Lower
numbers are higher in priority than higher numbers, and the same goes
for letters lower in the alphabet. Grades in the range `a' through
`m' only return an error message and header to the sender when an
error occurs. Grades in the range `n' through `z' return nothing to
the sender should an error occur. The precedence names recognized by
many BSD sendmail configurations are special-delivery, first-class,
and junk. Others are useful mainly for getting mail out of the local
machine or for communicating with other machines that run smail in a
similar configuration. The grade character for a message is available
in string expansions as the variable $grade. The default setting is:
special-delivery:9:air-mail:A:first-class:C:bulk:a:junk:n
hit_table_len (number, 241)
The length of the internal-address ``hit'' table. smail hashes
addresses into this table to prevent multiple deliveries to the same
address. Longer tables speed address hashing, at the price of a small
increase in the amount of memory used. NB, this value may be ignored
in the future.
host_lock_timeout (numeric, 30)
Set the time during which smail will attempt to lock a host's retry
file; this file is used to guarantee exclusive delivery to that thost.
If smail cannot lock the file within this time, then it leaves the
message in the queue, to be delivered later.
A number with no suffix indicates seconds. Suffixes can be added to
indicate a time multiplier: m indicates minutes, h indicates hours,
and d indicates days.
hostnames (string)
hostname (string)
A colon-separated list of names for the local host. This list,
together with the attributes uucp_host and more_hostnames, should
represent all possible names for the local host. Note that smail does
not recognize the name hostname as a name for the local host unless
that name is also set by one of the other hostname variables. If your
local host is in more than one domain or can gateway to more than one
level of domains, then this attribute should represent those names.
For a host in a registered domain in the UUCP zone, which is also in
the maps distributed over USENET, localhost.uucp should also be in the
list. The first value in hostnames is used internally as a special
``primary name'' for the local host.
Under COHERENT, this attribute is turned off by default. smail
computes the value of hostnames by pairing the local host's name, as
set in file /etc/uucpname, with every value set by attribute domains.
smail re-computes the default value each time you run it.
lock_by_name (Boolean, on)
If this variable is turned on, locking of the input spool file is
always based on lock files. Otherwise, an i-node--based locking
mechanism may be used, such as the BSD function flock() or lockf()
under System V or COHERENT. I-node--based locking is more efficient,
if available. However, lock files can be easily created by shell
scripts, which may be advantageous under some circumstances.
lock_mode (number, 0444)
log_mode (number, 0664)
The mode assigned to newly created mail-system log files.
logfile (string, /usr/spool/smail/log/logfile)
The file into which smail writes transaction messages and error
messages. If this file does not exist, smail creates it with the mode
set by variable log_mode.
max_hop_count (number, 20)
If the hop count for a message equals or exceeds this number, then any
attempt at remote delivery results in an error message being returned
to the sender. smail uses this mechanism to prevent infinite loops.
To set the hop count for a specific message, use smail's command-line
option -h. Otherwise, smail computes it from the number of Received:
fields in the message header.
max_load_ave (number)
For systems on which a load average can be computed, this attribute
sets the maximum load average at which mail will be delivered. If the
load average exceeds this number, smail saves incoming mail within the
input spool directory for delivery later. Under COHERENT, this
attribute is not set; therefore, smail does not compute the load
average, and always attempts to deliver mail.
max_message_size (number, 100k)
Set the maximum size of a message. smail truncates messages longer
than this. (This is not yet implemented; at present, smail sets
nolimit on the size of a message.)
message_buf_size (number, 100k)
The size of the internal buffer that smail uses to read and write
messages. The larger the value of this buffer, the fewer the number
of calls to read() are required to read the message, because the
entire message is always kept in memory. The default value is 100
kilobytes (100k).
message_id_field (string)
smail expands this attribute to form the field Message-Id: in a mail
message's header. This will be used if such a field does not already
exist in the header. The default value is:
Message-Id: <$message_id@$primary_name>
message_log_mode (number, 0644)
Each message has associated with it a unique file that contains a
transaction log for that message. This number sets the permissions
that smail gives this file when it creates it.
method_dir (string, methods)
If a method attribute for a router does not specify a path name that
begins with `/', smail prefixes this directory onto the path to form
the complete path for the method file. If this does not begin with
`/', smail assumes that it is in the directory set by attribute
smail_lib_dir (described below). See the description of the router
file for more information on method files.
more_hostnames (string, off)
A colon-separated list of host names. These host names are in
addition to any names that smail computed from the domains when
forming the value of the variable hostnames. Thus, it is useful for
specifying names that are not formed from the computed name for the
host.
Attribute more_hostnames can also be called gateway_names, because it
is often used to indicate the list of domains for which this machine
is a gateway.
nobody (string, nobody)
The default user. This variables defines permissions to use when no
other user is specified. Also, smail uses this user in some
conditions when it is not certain whether a set of actions can be
trusted, if performed under other, potentially more powerful users.
This should reference a login identifier that has little power to do
harm or access protected files.
paniclog (string, /usr/spool/smail/log/paniclog)
The name of the file onto which smail appends panic messages and other
important error messages. If this file does not exist, smail creates
it and assigns it the permissions specified by variable log_mode.
smail records in this log all errors that require human intervention,
such as configuration errors or directory-permission errors, that
prevent mail spooling or delivery.
When a configuration error occurs, smail usually moves the mail into a
special error directory under the input spool directory. This
prevents smail from again attempting to delivery the message until the
configuration error has been corrected.
Thus, you should regularly check both the panic log and the error
directory, especially after you have changed a configuration. When
the problem has been resolved, you can move the diverted messages back
into the spool directory, and smail will again attempt to deliver
them.
postmaster_address (string, root)
postmaster (string, root)
This attribute sets the default address of the postmaster. If the
address Postmaster is not resolved by any of the configured directors,
smail then uses this address.
qualify_file (string, qualify)
This variable names the file that contains the host-name qualification
information. If this does not begin with `/', smail assumes that it
is a subdirectory of the directory defined by the attribute
smail_lib_dir.
queue_only (Boolean, off)
If this flag is set, then smail does not deliver incoming mail
immediately. It only attempts delivery when it explicitly processes
the input queue, such as when you invoke it with command-line option -
q.
received_field (string)
smail expands this string to form the field Received: in a mail
message's header. It inserts this field into the header if the
``received'' attribute is not explicitly turned off for a transport.
The default value for received_field is:
received_field="Received: \
${if def:sender_host\
{from $sender_host by $primary_name\
${if def:sender_proto: with $sender_proto}\
\n\t(Smail$version #$compile_num) }\
else {by $primary_name ${if def:sender_proto:with $sender_proto }\
(Smail$version #$compile_num)\n\t}}\
id $message_id; $spool_date"
require_configs (Boolean, off)
If this option is turned off or is not set, then smail does not
require its configuration files to exist. This applies to the primary
and secondary configuration files, and the director, router, and
transport files (respectively, /usr/lib/mail/directors,
/usr/lib/mail/routers, and /usr/lib/mail/transports). If one of these
files does not exist, smail ignores it and instead uses its internally
compiled configuration. If, however, you turn on this attribute, then
if smail cannot find a configuration file whose file name is not null,
it displays a panic message and exits.
To set a configuration file's name to null, turn off the attribute
that names it. For example, to set the router file's name to null,
use the attribute -router.
retry_file (string, retry)
This names the file that contains the retry-control information. If
this name does not begin with `/', smail assumes that it is in
directory named by variable smail_lib_dir (described below).
retry_duration (interval, 5d)
This specifies the default period of time for which smail will attempt
to deliver a message. If the message cannot be delivered within this
period of time, smail assumes it is undeliverable, and sends a
``bounce'' message either to the sender or to the list's owner, should
there be one. A number with no suffix indicates seconds. Suffices
can be added to indicate a time multiplier: m indicates minutes, h
indicates hours, and d indicates days. Under COHERENT, the default is
five days.
retry_interval (interval, 10m)
If smail cannot connect to a given host, it will wait at least this
amount of time before it tries again. This applies to all messages
routed to the host in question, to help process a queue efficiently.
return_path_field (string, Return-Path: <$sender>)
smail expands this string into field Return-Path: in the mail-
message's header. It inserts this field into the header if attribute
return_path is turned on for a given transport in file
/usr/lib/mail/transports.
router_file (string, routers)
This attribute names the file that contains the router-configuration
information. If this does not begin with `/', smail assumes that it
is in the directory named by attribute smail_lib_dir (described
below).
second_config_file (string, none)
This names the secondary configuration file. The section on
configuration files, above, describes how this file relates to the
primary configuration file. If this file's name does not begin with
`/', smail assumes that it is in the directory named by attribute
smail_lib_dir (described below).
This is primarily useful in networks whose machines share file
systems. In particular, the attributes smart_user, smart_path, and
smart_transport are set in the secondary configuration file.
sender_env_variable (string, not set)
This attribute names the environmental variable that, in turn, gives
the name of the mail message's sender. Normally, the name of the
sender is determined from her login identifier, or by checking calling
process's real-user identifier. If sender_env_variable is set and the
environmental variable it names exists, then smail uses that name by
default. For example, if the line
sender_env_variable=BOGUS_NAME
appears in /usr/lib/mail/config, and if variable BOGUS_NAME is set in
the user's environment, then smail uses that name to identify the
sender, instead of the name for that user that appears in file
/etc/passwd.
smail (string, /bin/smail)
This attribute names the smail binary. smail uses this to re-exec
itself when a major configuration change has been detected, or to exec
smail when delivering error messages. If this name does not begin
with `/', smail assumes that this binary is kept in the directory
named by attribute smail_lib_dir.
smail_lib_dir (string, /usr/lib/mail)
This attribute gives the full path name of the directory in which
smail by default seeks its configuration files.
smail_util_dir (string, /usr/lib/mail)
This attribute gives the full path name of the directory that holds
smail's utilities, in particular the utilities mkaliases and mkdbm.
smart_path (string, not set)
This attribute defines the value that the router smarthost uses by
default for its path attribute. It gives the path to a machine whose
routing data base is more complete than the one on your local host.
By default, this is not set; however, if you using UUCP to receive
mail service from another system, you must set this variable to the
name of that system. For details, see the Lexicon entry for routers.
smart_transport (string, not set)
This attribute defines the value that the smarthost router driver uses
by default for its attribute transport. For details, see the Lexicon
entry for routers.
smart_user (string, not set)
This attribute defines the value that the smarthost router driver uses
by default for its attribute smart_user. For details, see the Lexicon
entry for routers.
smtp_accept_max (number, 20)
This attribute sets the maximum number of SMTP connections that smail
will process at any one time. This is for use with SMTP daemons
started with smail's command-line option -bd, or through the command
smtpd. If smail receives a a connection request when this number of
SMTP-connection children have already been forked, smail shuts down
the connection with SMTP message 421. If this attribute is set to
zero, then the number of SMTP connections is unlimited.
smtp_accept_queue (number, 5)
If this number of SMTP connection processes is exceeded, then smail
accepts additional connections but queues their messages for later
processing. When the number of current connection processes drops
below this number, smail resumes the immediate processing of mail (if
attribute delivery_mode is set to foreground or background.) If
delivery_mode is set to zero, then smail will always process mail
immediately, regardless of the number SMTP connections that it is
handling. Note that the value of smtp_accept_queue should be less
than the value of smtp_accept_max. Setting smtp_accept_max to zero
prevents smtp_accept_queue from working correctly in all cases.
smtp_banner (string)
smail expands this string to the SMTP startup banner. smail's SMTP
server writes this banner when it accepts a connection request. Each
line of this message is automatically preceded by identification code
``220''; newlines are correctly changed into a carriage-return newline
sequence. The default value for smtp_banner is:
$primary_name Smail$version #$compile_num ready at $date
smtp_debug (Boolean, on)
This Boolean variable controls the meaning of the DEBUG command when
receiving SMTP commands. If this variable is on, then the DEBUG
command (with an optional debugging level) sets debugging to the
specified level, or to level 1 if no level was specified. smail
writes the debugging output to the SMTP connection.
smtp_receive_command_timeout (interval, 5m)
This attribute sets the time that smail's SMTP daemon waits for a
receiver command after it displays its prompt. If the daemon does not
receive the command within this interval, it closes down the
connection and exits. The default is 5m, that is, five minutes.
smtp_receive_message_timeout (interval, 2h)
This attribute sets the time that smail SMTP daemon waits for a
message after it has displayed its prompt:
354 Enter mail
If it does not receive the entire message within this interval, it
removes the message, closes the connection, and exits. The default is
2h, that is, two hours.
spool_dirs (string, /usr/spool/smail)
This sets the directory or directories into which smail spools
incoming mail. If it names more than one directory, the directories
must be separated by a colon `:'. If smail cannot write a message to
the first directory (say, due to permission problems, file-system-full
errors, etc.), it tries to write the message into the other
directories, one after another, until it either succeeds in writing
the message or runs out of directories to try. Each spool directory
is expected to have the following writable subdirectories:
input The actual spool files
lock Temporary lock files
msglog Temporary per-message transaction logs and audit trails
error Messages failing from problems requiring human intervention
spool_grade (character, C)
This attribute gives the default grade for mail messages. It can be
overridden by a Precedence: field in a message's header. smail uses
the grade to sort messages in the input spool directory. The grade is
also available in string expansions as the variable $grade. See the
description of the attribute grades, above, for more information.
spool_mode (number, 0440)
This attribute sets the permissions smail gives to spooled files.
transport_file (string, transports)
This attribute names the file that holds the transport-configuration
information. If the directory does not begin with `/', smail assumes
it is in the directory named by the attribute smail_lib_dir (described
above).
trusted_users (string, off)
This names the users who are trusted to specify a sender for a
message. Users who are not in this list cannot specify a Sender:
field in a mail header; if they do, smail removes it. If a trusted
user specifies a From: header field, then smail also creates a Sender:
field that names the real user who submitted the message.
In general, this attribute should name every user under whom remote
mail is received and sent to smail. If this list is turned off, using
the form -trusted, then every user is trusted.
NB, smail uses the real user identifier to verify a trusted user.
However, the program uucico runs under the real user identifier of the
user who invoked it -- and any user can invoke uucico. smail cannot
distinguish this case from any other, and thus will do the ``wrong
thing'' in this instance. Under COHERENT, this attribute is turned
off by default to avoid this problem.
trusted_groups (string, off)
This attribute names the user groups that are trusted to specify a
sender of a message. smail checks a user's effective group identifier
to ensure that he really is a member of a trusted group. Thus, were
smail a setgid program, then this string would be of no value and
should be turned off. However, if smail is not set gid (as it is not
under COHERENT), then programs that invoke smail under a specific
effective gid, not a specific real uid, can be detected and can be
properly treated as trusted.
uucp_name (string)
This attribute gives the name of your local host. It is computed at
run-time. This name is available in string expansions as the variable
$uucp_name smail also uses it in the ``remote from hostname'' suffix
to ``From'' lines for mail being delivered to remote machines, when
the from attribute is turned on for a transport.
visible_domains (string)
This is a synonym for attribute domains.
See Also
Administering COHERENT,
directors,
mail [overview],
routers,
smail,
transports
Notes
Copyright © 1987, 1988 Ronald S. Karr and Landon Curt Noll. Copyright
© 1992 Ronald S. Karr.
For details on the distribution rights and restrictions associated with
this software, see file COPYING, which is included with the source code to
the smail system; or type the command: smail -bc.
