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sendmail.m4(8)
NAME
sendmail.m4 - Introduction to using m4 macros to create a sendmail.cf
configuration file
OPERANDS
The following list provides definitions of the operands used in the
configuration files. The operands appear in the recommended usage order.
define(_ParentDomain, {yyy.xxx})dnl
This macro specifies the name of the next-highest domain above your own
(yyy.xxx). It is used to determine which hosts you can send mail to
that might be close enough to be reached directly, and to figure out
where MyDomains are located.
define(_MyDomains, {domain... })dnl
This macro specifies the list of all the domains under ParentDomain
that are aliases for your own. It is a list of single tokens separated
with blanks. These are qualified under ParentDomain in actual use.
You must include the single-token component of MyDomain. For example,
if the ParentDomain is ECD.COM and MyDomain is AP.ECD.COM, then
MyDomains must include at least the token AP. This operand is used in
conjunction with the _MailHub operand.
define(_MyDomain, {domain.}_ParentDomain)dnl
This macro specifies the fully-qualified domain that you are in. It
must end in _ParentDomain.
If you set both MyDomain and ParentDomain to the string LOCAL, sendmail
assumes that you do not have a domain, but instead use single-token
hostnames (which can include dashes and underscores but not dots) and
that you are using /etc/hosts or NIS, but not BIND.
define(_MyNicknames, {})dnl
This macro is used to initialize the $=w operand. If your host is
known by several names inside of _MyDomain, you must put the first
token of all names (optionally including the first token of your
/bin/hostname) into this list.
In a TruCluster Server cluster, you should also specify the cluster
alias and the unqualified hostnames of all the members of the cluster.
define(_exportedName, _MyDomain)dnl
This macro specifies the domain name (@DOMAIN) appended to any mail
address that leaves the local domain and does not have a domain name in
its address. (For example, local user names do not have the domain
name in the address.)
Usually, _MyDomain is specified; therefore, the mail leaves the domain
with a host name (such as, wicked@AP.ECD.COM) even though there is no
such host.
If you do this, you need an MX RR at the root ("@") of the domain that
points to some set of mail servers whose MyDomain's variables include
your domain. This is irrelevant if you are using LOCAL for MyDomain
and ParentDomain.
define(_MailCluster, {T})dnl
Use this macro if you are using rdist, or NIS to ensure that all
aliases on all machines in your local domain are equivalent. (They do
not need to have the same values, but the same alias names must be
present on all machines.)
Note
It is recommended that you use this macro, unless you have specific
reasons for not using it.
If you use this macro, mail sent to @MyDomain is treated as local mail,
which means that any host in the domain can strip off the @MyDomain and
search its aliases database to decide what to do with the message.
Mail sent to other hosts in the local domain with MailCluster turned on
will have the hostname (rather than ExportedName) appended to the
username. Because it is local mail, you know it came from some host in
the local domain and you presumably want to know which host.
Note
Setting ExportedName to MyDomain and turning on MailCluster, creates
an environment where all mail names are equivalent on all hosts in
the domain. This simplifies the address formats for all local mail.
define(_MailHub, {T})dnl
You use this macro if your machine recognizes mail to user@localdomain
and therefore can access anyone's mailbox (usually through an aliases
file containing the real mailboxes for everyone who might receive such
mail). A Mail Hub treats all mail to user@localdomain as local mail by
using the aliases file.
This is different than a Mail Cluster, where every host acts as a Mail
Hub (by virtue of everyone having the same "all knowing" aliases file).
define(_QueueDir, {directory})dnl
This macro specifies the mail spool location (which is usually
/var/spool/mqueue). Note that there is no advantage to using
/usr/spool/mail for this if that is a symlink to /var/spool/mail.
Using the correct names and avoiding symlinks is recommended.
define(_TrustedUsers, {list})dnl
This macro specifies the list of user names that are allowed to run
sendmail with the -f option that sets the envelope sender address.
There are users that have a legitimate need to use the -f; however, for
security reasons, it is recommended that only those users be allowed
that option.
define(_NonHiddenUsers, {list})dnl
This macro specifies the list of users that have the @hostname of the
sending host added to their From: line, if they send mail to some other
host in the local domain. This procedure is performed regardless of
the MailCluster and MailHub.
define(_UnqualifiedW, {T})dnl
This macro sets the unqualified hostname.
This macro is not required. Under Tru64 UNIX sendmail it is recommended
that you do not use this operand.
define(_TagPOP, {T})dnl
This macro enables your machine to recognize POP customers as
username.POP. This is preferable to HostPOP. as shown in the following
example. If you use this macro, you must format your aliases as
follows:
username:username.POP
Instead of the following format:
username:username@POP
Be aware that older versions of the popaka utility create the @pop
style address. If you want to change, turn both TagPOP and HostPOP on
and wait for a new popaka utility, at which point you can shut off
HostPOP.
define(_HostIMAP, {T})dnl
This macro enables your system to be able to recognize IMAP customers
as username@IMAP. Older popaka utilities generate aliases in this
form. If you are using an older version of the popaka utilities, you
can enable HostIMAP. However, you will not be able to name any host in
your domain "IMAP" because it would conflict with the sendmail.cf
file's internal meaning for the @IMAP string. It is recommend that you
use TagIMAP.
define(_DECNet, {T})dnl
This macro enables you to recognize DECnet-style addresses or to
communicate with DECnet.
define(_DollarY, {})dnl
This macro only applies to DECnet. You use this macro to define this to
your DECnet node name if your sendmail binary does not define $=y as
the result of DECnet's getnodename() call. If you have such a binary,
it is best not to define this variable because that way you can share a
single sendmail.cf file across all of your DECnet nodes. Otherwise you
need to build a separate sendmail configuration file for DECnet node,
just to set $=y. Tru64 UNIX automatically defines $=y if DECnet's
installed.
define(_UTK_Mail11, {T})dnl
This macro applies to DECnet only. You can use this macro, if you are
using the UTK Mail11 package.
define(_UUCP, {T})dnl
This macro enables your system to recognize UUCP addresses. If you do
not also define _GateUUCP, you must run UUCP on your host. In most
cases, mail with UUCP addresses is relayed to a host that recognizes
UUCP addresses to process the address.
define(_POP, {T})dnl
This macro enables your system to recognize POP customers.
define(_RFC976, {})dnl
This macro instructs sendmail to format your headers in RFC 976 format.
For example:
From: waxie@ap.ecd.com (Paul Waxie)
If you use this macro, you should define this to be T.
define(_TransDomain, {transport})dnl
define(_GateDomain, {})dnl
These macros control how mail that is destined for some other host in
your local domain is handled.
TransDomain is the transport used to reach other hosts or to reach the
designated gateway (usually smtpl which specifies local SMTP).
If you decide to route all such local-domain mail through a gateway,
then specify the name of the gateway in GateDomain. If you want the
mail to go directly to the gateway, do not specify anything for the
GateDomain operand.
In practice, TransDomain is always set to smtpl and GateDomain is
always either null or the name of your local mail hub. However, there
is no penalty for sending local mail directly between workstations and
no advantage for sending such mail through your mail hub. Using a
gateway is not recommended for local mail.
define(_TransParent, {smtp})dnl
define(_GateParent, {})dnl
These two macros perform the same functions as TransDomain and
GateDomain except that they control mail which is sent to the parent
domain rather than to the local domain.
In most domains, there are no security filters that restrict SMTP
traffic between hosts in the domain. If that is true in your domain
then it is recommended that you set TransParent to smtp and set
GateParent to null string.
As with local-domain mail, there is no real advantage to using a
gateway for local mail.
define(_TransINET, {transport})dnl
define(_GateINET, {host.}_MyDomain)dnl
These macros specify the transport to be used and the gateway host for
mail leaving the domain.
If you are directly connected to the Internet, then you can set
TransINET to smtp and leave GateINET empty.
If you need to use a gateway to reach the Internet, then set TransINET
to the protocol used by the gateway (uucp, mail11, or smtp) and set
GateINET to the name of the host you will reach through that transport.
That host will presumably deliver your mail to its ultimate recipient
or forward it to another host that will deliver the mail or forward it
on.
If you leave GateINET empty, then TransINET is ignored because it must
be the local smtp transport.
define(_TransUUCP, {transport})dnl
define(_GateUUCP, {host.}_MyDomain)dnl
These macros specify the transport and the gateway for UUCP mail. Note
that if GateUUCP is empty, then TransUUCP is ignored since the local
uucp transport must be used. In which case uux is used as the
transport.
You might set TransUUCP to smtpr. GateUUCP host has aliases for all of
your users. This permits outbound UUCP addresses to omit your local
host name.
define(_MyUUCPnameList, {host})dnl
This macro specifies the UUCP host name for all of the members of your
TruCluster Server cluster running the UUCP protocol. Use this macro if
you are running UUCP on your system. See protocols.map(4) for more
information.
define(_UuxArgs, {options})dnl
This macro specifies the arguments for UUCP. For a complete list of the
possible options, see uux(1).
define(_GateUsenet, {host.}_MyDomain)dnl
This macro specifies the name of a host on your network that is capable
of accepting mail sent to the USENET.
If there is no such host on your network, leave this macro empty.
Note that Tru64 UNIX does not currently include the software necessary
on the receiving host, because it varies according to whether you are
running C News or B News or INN.
define(_AddMail11Cl, {pseudodomain})dnl
This macro applies to DECnet mail only. If your users or your inbound
mail11 listener puts a pseudodomain name other than .DNET on incoming
addresses, sendmail needs to know.
define(_TransIV, {transport})dnl
define(_GateIV, {}) dnl
This macro applies to DECnet only.
If GateIV is set to an empty string, then sendmail attempts to deliver
the mail directly using TransIV (which is almost always smtp).
If you have MX RRs for all of your mail11 hosts then you can use SMTP
to reach them or at least the closest relay host.
If GateIV is set to a fully qualified host name, then TransIV is used
to forward the mail to that host, unless GateIV is set to the same
hostname. In this case the mail11 mailer is called directly.
This lets you share a sendmail.cf file across all of your workstations
and mail11 gateway machines, because the mail will go to the designated
mail11 gateway first, which, on forwarding, the mail will recognize its
own name as the designated gateway and instead call the mail11
transport.
It is recommended that you set TransIV to smtpr if the GateIV host has
aliases for all of your users. This enables outbound DECnet addresses
to omit the local host name.
define(_PhaseIVdomain, {pseudodomain})dnl
This macro applies to DECnet only.
Mail from a DECnet node is always encapsulated in a pseudodomain. The
DECnet pseudodomain is an arbitrary string that should be used
uniformly by your site or organization. The DECnet pseudodomain must
always appear after the parent domain. For example, in the following
domain name, QNET is the DECnet pseudodomain portion of the domain
names:
NODEONE.QNET.ECD.COM
NODETWO.QNET.ECD.COM
PhaseIVdomain is the non-qualified name of the pseudodomain. It is
always qualified with ParentDomain before being emitted into the
Internet.
This can be anything you want but is usually the name of the DECnet
network. Do not set this to DNET. Set it to the proper name of your
network, not the name of the network's technology.
define(_MyIVnameList, {})dnl
This macro specifies the Phase IV node names of the nodes in your
TruCluster Server cluster. Use this macro only if your node is running
DECnet.
define(_MyIVaddrList, {})dnl
This macro specifies the Phase IV node address. Use this macro only if
your node is running DECnet.
define(_Mail11path, {/usr/sbin/mail11v3})dnl
This macro applies to DECnet only.
This macro specifies the location of the mail11 binary. For this
operating system it is located in /usr/sbin/mail11v3.
define(_ReversePhaseIV, {})dnl
This macro applies to DECnet only.
Unnamed DECnet nodes are reachable through the AA.NNN:: notation. The
AA in this case is actually of higher precedence than the NNN. You may
want to reverse the order when rewriting into Internet form because
Internet addresses have higher precedence toward the right side.
Whatever you do, you must do it consistently across all mail11 gateways
in your network, and you will probably not be able to change your mind
later.
define(_PhaseVns, {})dnl
This macro applies to DECnet only.
This macro applies to DECnet Phase V only. It specifies the namespace
that sendmail assumes for any mail it receives in without a namespace,
if you are running DECnet Phase V. It is recommended that you make it
the name of the namespace you are in. If you are running DECnet Phase
IV, you must get the name of the namespace from your network
administrator.
define(_TransV, {transport})dnl
define(_GateV, {gateway})dnl
define( _PhaseVdomain, {pseudodomain})dnl
These macros apply to DECnet Phase V only. They specify the transport,
gateway, and pseudodomain for DECnet Phase V mail.
Note that Phase V names are always reversed so there is no
ReversePhaseV variable.
define(_MyVnameList, {})dnl
This macro specifies the Phase V node names of the nodes in your
TruCluster Server cluster. Use this macro only if your node is running
DECnet.
define(_UMC, {})dnl
This macro enables your system to MR or UMC addresses. If you do not
define GateMsgRout you must run UMC on your host. Most hosts use a
gateway to reach MR.
define(_TransMR, {transport})dnl
define(_GateMR, {gateway.}_MyDomain)dnl
define(_MsgRoutDomain, {pseudodomain})dnl
This macro applies to DEC MessageRouter (mail-plus) only. They define
the transport, gateway, and pseudodomain.
define(_GateMsgRoutCl, {list})dnl
This macro applies to the DEC MessageRouter (mail-plus) only. It
specifies other pseudodomains that the software or your users may use,
expecting them to be recognized as Message Router pseudodomains.
define(_IDA, {T})dnl
Use this macro if you have an IDA version of sendmail. This turns on
split rewrite rules (O/). It also allows for local aliases lookup. If
you are usingTru64 UNIX's sendmail utility, it is recommended that you
set this operand to be T.
define(_AliasesLocal, {T})dnl
This macro specifies that aliases in your local aliases file are
_NonHiddenUsers. You must have _IDA defined because it uses IDA
features to do the aliases lookup. See the explanation of
_NonHiddenUsers and _IDA.
define(_RelayAll, {})dnl
This macro specifies to bypass most of the other routing options (for
example, GateDomain) and forces your mail to be sent by _TransINET to
your _GateINET machine. This allows workstations with simple mail
configurations to create mail locally, but have it appear as if it came
from the main relay (GateINET) machine. Using this option can simplify
things for the system administrator, by funneling all mail through
central, well-maintained machines.
The only mail that is delivered locally (to the simple workstation) is
the mail addressed to the user names contained in _NonHiddenUsers.
define(_Cluster, {})dnl
This macro enables sendmail to work in a TruCluster Server cluster
environment. Set it to T if your system is part of a cluster.
define(_ClusterAlias, {})dnl
This macro specifies the alias for your TruCluster Server cluster. Use
it only if your system is configured as part of a cluster.
define(_MyUnqualNameList, {})dnl
This macro specifies the unqualified names of the nodes in your
TruCluster Server cluster that can handle X.25 (PSI) mail. Use this
macro only if you are running X.25 on your system.
define(_LDAPMap, {})dnl
This macro specifies that sendmail will use an LDAP server to resolve
aliases. If you intend to use LDAP, set this macro to T. See
Lightweight Directory Access Protocol for more information.
define(_LDAPParam, {})dnl
This macro defines the map type and LDAP search string for sendmail to
specify when it contacts an LDAP server for alias resolution. The map
type is ldapx.
The sendmail command supports most of the standard map options as well
as options specific to LDAP. The following LDAP options are the ones
most users need, but you can specify additional parameters depending on
your application.
You must specify arguments for each LDAP option as strings, therefore,
you must enclose the arguments in double quotes ("). Also, the
arguments must immediately follow the associated LDAP option, that is,
leave no space between options and double quotes.
-b"ldap_search_base"
LDAP base Distinguished Name (DN) search string
-h"ldap_server_list"
LDAP server's host name list. This contains the list of server
names to use for an LDAP search. The list of names is separated by
white space.
-k"search_attributes"
String containing a list of attribute/value pairs for which to
search in the LDAP database. The syntax for each pair is
attribute=%s, where %s is the token for which to search.
If you need to specify more than one attribute/value pair, you must
enclose each pair in parentheses (). In addition, you must begin
the string with (|). For example:
"(|)(attr1=%s)(attr2=%s)(...)(attrN=%s)"
You can specify up to 1024 attribute/value pairs.
-v{"return_attribute"}
String containing a list of comma-separated attributes for which to
return values. For each LDAP record that matches the
attribute/value pairs you specify in the -k option, the LDAP server
returns the corresponding attribute you specify with the -v option.
The brackets {} are necessary to tell the m4 command to treat the
double quotes as literal; otherwise, the quotes are not preserved
in the sendmail.cf output file.
For example, assume your LDAP base DN is compaq, your LDAP server name
is ldap.site.com, the search attribute is mailaddr, and the return
attribute is forwardAddr. You would specify the _LDAPParam macro as
follows (the backslash indicates line continuation):
define(_LDAPParam, {ldapx -b"o=compaq" -h"ldap.site.com" \
-k"(mailaddr=%s)" -v{"forwardAddr"}})dnl
DESCRIPTION
The mailsetup script enables you to create new mail configurations. If you
have experience creating sendmail.cf configuration files or your system
requires specialized configuration files, you might want to create your
configuration files manually.
Use the macros described in this reference page to generate a configuration
file. You should save your configuration file under the name hostname.m4,
where hostname is the name of your system or the alias for a TruCluster
Server cluster.
After you create the m4 file with the operands you need, you can generate
the sendmail.cf file by issuing the following command:
# m4 -D_Configfile=hostname.m4 sendmail m4 > sendmail.cf
You must be in the /var/adm/sendmail directory to use this command.
The sendmail.m4 package used byTru64 UNIX provides the following functions:
· Rewrites addresses, encapsulating mail from non-Internet protocols
(for example, DECnet) within pseudodomains. This helps to ensure that
replies are sent back to the correct address, where they can be
handled appropriately.
· Performs routing, based on the domain to which the mail is sent.
· Supports multiple return address formats, including domain-based
addresses. For example, a host with the name myhost.mysite.ecd.com
would normally format a user's mail address as
user@myhost.mysite.ecd.com, or user@cluster_alias.mysite.ecd.com in a
TruCluster Server cluster (which changes the address only for SMTP).
By using the _ExportedName operand, you can set the return address to
be mysite.ecd.com. By using the _MailHub and MyDomain operands, your
mail system recognizes the phrase mysite.ecd.com as a synonym for this
host.
The dnl command is "delete to newline" command and causes the m4 compiler
to ignore the dnl characters and all text that follows it, up to and
including the end of line. If you do not follow a define command with a
dnl command, then the newline after the right parenthesis ()) is emitted
into the output (which is a sendmail.cf file).
Blank lines are permitted in the sendmail.cf file; however, they are
unnecessary and not recommended.
Braces ({}) are used as quoting characters. You can use them even when
they are not required.
Note that null definitions have the following of the form:
define(Operand, {})
The only rule you must follow in creating the configuration m4 file is to
surround literal text with braces ({}); however, you must leave macro names
(which you presumably want expanded by m4) unquoted. (That is, do not
enclose macros that you want expanded in braces ({}).)
Mailers
The sendmail program invokes a mailer to handle your mail. Usually, this is
local (for local delivery on the host), smtp (standard SMTP), smtpl (SMTP
local), or smtpr (SMTP to relay) for delivery over the Internet. These
mailers (smtp, smtpl, and smtpr) invoke SMTP to deliver the mail; however,
they differ in how they rewrite the return address. If you are in doubt as
to which mailer to use, it is safest to use smtp.
The smtp mailer qualifies your mail with the ExportedName operand, except
for mail sent from NonHiddenUsers or from an alias (if AliasesLocal is
true).
The smtpl mailer handles mail sent within you local domain. This mailer is
used when mail is sent to users within the local domain. Depending on how
the _MailCluster and _NonHiddenUsers operands are defined, the hostname is
removed from the return address before the mail is sent.
The smtpr mailer always removes the hostname, except for _NonHiddenUsers.
This is useful when the relay machine is a mail hub and has aliases for all
users in your mail system.
Routing
The sendmail.m4 package performs some routing decisions based on the domain
in which the address ends. In general, you can configure your system to
check for some special cases (for example, DECnet or UUCP style addresses).
If the address does not conform to any of the cases specified, it will
check to see if the mail resides in your local domain (_GateLocal), parent
domain (GateParent), or is outside your local network (GateINET). You can
configure your system to pass mail to and from the Internet by setting the
_GateINET operand to the name of the Internet gateway on your local network
and leaving the GateDomain and GateParent operands blank.
Lightweight Directory Access Protocol
The sendmail command supports the Lightweight Directory Access Protocol
(LDAP) for alias resolution. LDAP is an open protocol for accessing
directory services. An LDAP server provides information, such as email
addresses and public keys, to applications running on client systems.
Usually, when sendmail parses a recipient's address and determines that the
address is local, it looks up the address to determine if there are any
aliases associated with it (see aliases(4)). If sendmail does not find an
alias, it looks in the .forward file in the recipient's home directory to
see if the recipient has any personal aliases. While this works well for a
single system, it becomes cumbersome to maintain in a distributed
environment. Performance suffers if the list of aliases becomes too large.
With LDAP as another means for storing user alias information, sendmail can
share aliases in a distributed fashion, and as a result, system
administrators do not have to maintain several databases. Furthermore,
because there are fewer databases and the LDAP servers that serve them are
typically dedicated machines, address resolution is more efficient. (Note
that the sendmail command itself requires a fair amount of resources, and
performing alias resolution on the same system can be costly.)
To configure sendmail with LDAP, set the _LDAPMap operand to {T} and
specify the LDAP search string in the _LDAPParam operand. The appropriate
map line and rules are added to the system sendmail.cf file. This tells
sendmail to perform an LDAP lookup for the receipient's address in addition
to the standard alias and .forward lookup. If no matches are found, the
recipient address is considered to be local to this system.
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