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sendmail.m4(8)
NAME
sendmail.m4 - Introduction to using m4 macros to create a sendmail.cf
configuration file
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 may want to create your
configuration files manually.
The macros described in this reference page can help you generate a
configuration file manually. These parameters are then used as input to
generate a new sendmail.cf. It is suggested that you save different
configurations under the name hostname.m4 (where hostname is the name of
your system) or some other suitable mnemonic.
After you create the m4 file with the parameters you want, 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 by DIGITAL 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 the mail address as user@myhost.mysite.ecd.com.
By using the _ExportedName parameter, you can set the return address
to be mysite.ecd.com. By using the _MailHub and MyDomain parameters,
your mail system recognizes the phrase mysite.ecd.com as a synonym for
this host.
· Supports optionally stripping off host names for mail sent within your
local domain, leaving the unqualified user name. This feature can
improve the readability of mail sent within your local domain.
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(Parameter, {})
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 parameter, 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 parameters 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 parameter to the name of the Internet gateway on your local
network and leaving the GateDomain and GateParent parameters blank.
PARAMETERS
The following list provides definitions of the parameters used in the
configuration files. The parameters 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
parameter is used in conjunction with the _MailHub parameter.
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 parameter. 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.
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 insure 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. Also, setting this variable will cause mail sent between
hosts in the local domain to have no @hostname appended to any
address, which is beneficial to the readability of local mail headers.
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 a mail cluster 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 flag 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 DIGITAL UNIX sendmail it is
recommended that you do not use this parameter.
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. DIGITAL 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 parameter.
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(_MyUUCPname, {host})dnl
This macro specifies the UUCP host name for your system. Use this
macro only if you are running UUCP on your system.
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 DIGITAL 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(_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(_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 using DIGITAL UNIX's sendmail utility, it is recommended
that you set this parameter 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.