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<HTML>
<HEAD>
<!-- This HTML file has been created by texi2html 1.52
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<TITLE>Exim Specification - 40. The default configuration file</TITLE>
</HEAD>
<body bgcolor="#FFFFFF" text="#00005A" link="#FF6600" alink="#FF9933" vlink="#990000">
Go to the <A HREF="spec_1.html">first</A>, <A HREF="spec_39.html">previous</A>, <A HREF="spec_41.html">next</A>, <A HREF="spec_59.html">last</A> section, <A HREF="spec_toc.html">table of contents</A>.
<P><HR><P>
<H1><A NAME="SEC780" HREF="spec_toc.html#TOC780">40. The default configuration file</A></H1>
<P>
<A NAME="IDX1715"></A>
<A NAME="IDX1716"></A>
The default configuration file supplied with Exim as <EM>src/configure.default</EM> is
sufficient for a single host with simple mail requirements. It contains
comments about options you might want to set, but which it lets default,
together with the settings described here.
</P>
<P>
<H2><A NAME="SEC781" HREF="spec_toc.html#TOC781">40.1 Main configuration settings</A></H2>
<P>
There are four explicit options in this section:
<PRE>
never_users = root
</PRE>
<P>
This prevents Exim from ever running as root when performing a local delivery.
Instead, it runs as `nobody'.
<font color=green>
<PRE>
host_lookup = *
</PRE>
<P>
</font>
<A NAME="IDX1717"></A>
<A NAME="IDX1718"></A>
This specifies the sending IP networks for which a DNS reverse lookup is done,
in order to get the host name from the IP address of an incoming message. The
default setting matches all IP addresses. The host name appears in the log and
in messages' <EM>Received:</EM> headers.
</P>
<PRE>
forbid_domain_literals
</PRE>
<P>
This locks out the use of `domain literal' addresses such as
<PRE>
root@[192.168.35.43]
</PRE>
<P>
at the syntactic level. Although still specified in the RFCs, such addresses
are not of great relevance in today's Internet, are not understood by many
people, and have been abused by spammers seeking open relays.
</P>
<P>
<font color=green>
<PRE>
timeout_frozen_after = 7d
</PRE>
<P>
This option causes Exim to abandon frozen messages after they have been on its
queue for a week.
</font>
</P>
<P>
As the <EM>primary_hostname</EM>, <EM>qualify_domain</EM>, and <EM>local_domains</EM> options are
not specified, they all take the name of the local host, as obtained by
the <EM>uname()</EM> function, as their value.
</P>
<P>
No relaying is permitted through the host, because neither <EM>relay_domains</EM> nor
<EM>host_accept_relay</EM> is set. See chapter 46 for more details
about relay control.
</P>
<H2><A NAME="SEC782" HREF="spec_toc.html#TOC782">40.2 Transport configuration settings</A></H2>
<P>
Four local transports and one remote transport are defined. The first one is
the remote transport:
<PRE>
remote_smtp:
driver = smtp
</PRE>
<P>
This transport is used to do external deliveries over SMTP, with default
options.
The first local transport is
<PRE>
local_delivery:
driver = appendfile
file = /var/mail/$local_part
delivery_date_add
envelope_to_add
return_path_add
</PRE>
<P>
This is set up to deliver to local mailboxes in a traditional `sticky
bit' directory. Some installations prefer not to set the `sticky bit', but
instead run the delivery under a specific group, with the directory being
writeable by the group. Adding the following options achieves this:
<PRE>
group = mail
mode = 0660
</PRE>
<P>
To deliver into files in users' home directories, a setting such as
<PRE>
file = /home/$local_part/inbox
</PRE>
<P>
or
<PRE>
file = $home/inbox
</PRE>
<P>
should be substituted for the default <EM>file</EM> option. The three options ending
in <EM>_add</EM> cause Exim to add three header lines to the message as it writes it
to the mailbox. They can be removed if these headers are not required. The
second local transport is
<PRE>
address_pipe:
driver = pipe
return_output
</PRE>
<P>
This transport is used by Exim when a local part that is expanded via an alias
or forward file causes delivery to a pipe.
Any output from the pipe is returned to the sender
of the message. The third local transport is
<PRE>
address_file:
driver = appendfile
delivery_date_add
envelope_to_add
return_path_add
</PRE>
<P>
This transport is used by Exim when a local part that is expanded via an alias
or forward file causes delivery to a specified file
(by generating a path name not ending in `/'). The final local transport is
<PRE>
address_reply:
driver = autoreply
</PRE>
<P>
This transport is used by Exim when a local part that is expanded via a filter
file causes an automatic reply to a message to be generated.
</P>
<H2><A NAME="SEC783" HREF="spec_toc.html#TOC783">40.3 Director configuration settings</A></H2>
<P>
Three directors are specified for the default configuration. Note that the
order of director definitions matters. The first director causes local parts to
be checked against the system alias file, which is searched linearly:
<PRE>
system_aliases:
driver = aliasfile
file = /etc/aliases
search_type = lsearch
file_transport = address_file
pipe_transport = address_pipe
</PRE>
<P>
If an alias generates a file or pipe delivery, the <EM>address_file</EM> or
<EM>address_pipe</EM> transport is used, as appropriate.
The second director comes into play if a local part does not match a
system alias:
<PRE>
userforward:
driver = forwardfile
file = .forward
no_verify
no_expn
check_ancestor
# filter
file_transport = address_file
pipe_transport = address_pipe
reply_transport = address_reply
</PRE>
<P>
An attempt is made to look for a file called <TT>`.forward'</TT> in the home directory
of a local user. However, this director is skipped when verifying addresses or
running an SMTP EXPN command. The <EM>check_ancestor</EM> option prevents a
<TT>`.forward'</TT> file from turning a login name back into a previously-handled alias
name. The <EM>filter</EM> option is commented out in the default configuration. Thus
<TT>`.forward'</TT> files are treated in the conventional manner, but filtering can be
enabled by removing the # character.
</P>
<P>
If forwarding or filtering generates a file, pipe, or autoreply delivery, the
<EM>address_file</EM>, <EM>address_pipe</EM>, or <EM>address_reply</EM> transport is used,
as appropriate.
The final director is
<PRE>
localuser:
driver = localuser
transport = local_delivery
</PRE>
<P>
This checks that a local part is the login of a local user, and if so, directs
the message to be delivered using the <EM>local_delivery</EM> transport.
</P>
<H2><A NAME="SEC784" HREF="spec_toc.html#TOC784">40.4 Router configuration settings</A></H2>
<P>
Only one router is defined in the default configuration:
<PRE>
lookuphost:
driver = lookuphost
transport = remote_smtp
</PRE>
<P>
Its default settings cause it to look up the domain in the DNS, in order to
determine the host to which a message should be sent, using the <EM>remote_smtp</EM>
transport.
</P>
<H2><A NAME="SEC785" HREF="spec_toc.html#TOC785">40.5 Default retry rule</A></H2>
<P>
A single retry rule is given in the default configuration:
<PRE>
* * F,2h,15m; G,16h,1h,1.5; F,4d,8h
</PRE>
<P>
This causes any temporarily failing address to be retried every 15 minutes for
2 hours, then at intervals starting at one hour and increasing by a factor of
1.5 until 16 hours have passed, then every 8 hours up to 4 days.
</P>
<H2><A NAME="SEC786" HREF="spec_toc.html#TOC786">40.6 Rewriting configuration</A></H2>
<P>
There are no rewriting rules in the default configuration file.
</P>
<H2><A NAME="SEC787" HREF="spec_toc.html#TOC787">40.7 Authenticators configuration</A></H2>
<P>
No authenticators are specified in the default configuration file. Note that in
order to use SMTP authentication, it is necessary to specify at least one
authenticator in <TT>`Local/Makefile'</TT>.
</P>
<P><HR><P>
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