sendmail.m4(8) System Manager's Manual 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. 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. 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 _Mail-
Hub operand. 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 sin-
gle-token hostnames (which can include dashes and underscores but not dots) and that you are using /etc/hosts or NIS, but not BIND.
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. 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. 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. 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 every-
one 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). 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 recom-
mended. 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. 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 Mail-
Cluster and MailHub. 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. 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 Host-
POP on and wait for a new popaka utility, at which point you can shut off HostPOP. 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. This macro
enables you to recognize DECnet-style addresses or to communicate with DECnet. 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. This macro applies to DECnet only. You can use this macro, if you
are using the UTK Mail11 package. 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. This macro enables your system to recognize POP customers. This macro instructs sendmail to format your head-
ers 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. 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. 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. 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. These macros specify the trans-
port 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. 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. This macro speci-
fies the arguments for UUCP. For a complete list of the possible options, see uux(1). 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. This macro applies to DECnet mail only. If your users or your inbound mail11 listener
puts a pseudodomain name other than on incoming addresses, sendmail needs to know. 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. 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. This macro specifies the Phase IV node names of the nodes in your TruClus-
ter Server cluster. Use this macro only if your node is running DECnet. This macro specifies the Phase IV node address. Use this
macro only if your node is running DECnet. 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. 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. 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. 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. 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. 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. This
macro applies to DEC MessageRouter (mail-plus) only. They define the transport, gateway, and pseudodomain. 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. 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. 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. 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 _NonHidde-
nUsers. This macro enables sendmail to work in a TruCluster Server cluster environment. Set it to T if your system is part of a
cluster. This macro specifies the alias for your TruCluster Server cluster. Use it only if your system is configured as part of a
cluster. 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. 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. 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. LDAP
base Distinguished Name (DN) search string 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. 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. String containing a list of comma-separated attributes for which to return val-
ues. For each LDAP record that matches the attribute/value pairs you specify in the -k option, the LDAP server returns the corre-
sponding 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 proto-
cols (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, includ-
ing 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 AliasesLo-
cal 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 sys-
tems.
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 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 appro-
priate 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 lookup. If no matches are found, the recipient address is considered to be local to this sys-
tem.
sendmail.m4(8)