path: root/debian/manpages/exim4-config_files.5

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.TH EXIM4-CONFIG_FILES 5 "Jan  4, 2015" EXIM4
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.SH NAME
exim4-config_files \- Files in use by the Debian exim4 packages
.SH SYNOPSIS
.br
/etc/aliases
.br
/etc/email\-addresses
.br
/etc/exim4/local_host_blacklist
.br
/etc/exim4/host_local_deny_exceptions
.br
/etc/exim4/local_sender_blacklist
.br
/etc/exim4/sender_local_deny_exceptions
.br
/etc/exim4/local_sender_callout
.br
/etc/exim4/local_rcpt_callout
.br
/etc/exim4/local_domain_dnsbl_whitelist
.br
/etc/exim4/hubbed_hosts
.br
/etc/exim4/passwd
.br
/etc/exim4/passwd.client
.br
/etc/exim4/exim.crt
.br
/etc/exim4/exim.key
.SH DESCRIPTION
This manual page describes the files that are in use by the Debian
exim4 packages and which are not part of an exim installation done
from source.
.SH /etc/aliases
is a table providing a mechanism to redirect mail for local
recipients. /etc/aliases is a text file which is roughly compatible
with Sendmail. The file should contain lines of the form
.br
name: address, address, ...
.br
The name is a local address without domain part. All local domains are
handled equally. For more detailed documentation, please refer to
/usr/share/doc/exim4\-base/spec.txt.gz, chapter 22, and to
/usr/share/doc/exim4\-base/README.Debian.gz. Please note that it
is not possible to use delivery to arbitrary files, directories and to
pipes. This is forbidden in Debian's exim4 default configuration.

You should at least set up an alias for postmaster in the /etc/aliases
file.
.SH /etc/email\-addresses
is used to rewrite the email addresses of users. This is particularly
useful for users who use their ISP's domain for email.

The file should contain lines of the form

.br
user: someone@isp.com
.br
otheruser: someoneelse@anotherisp.com

This way emails from user will appear to be from someone@isp.com to
the outside world. Technically, the from, reply\-to, and sender
addresses, along with the envelope sender, are rewritten for users that
appear to be in the local domain.

.SH /etc/exim4/local_host_blacklist
.I [exim host list]
is an optional file containing a list of IP addresses, networks and
host names whose messages will be denied with the error message
"locally blacklisted". This is a full exim 4 host list, and all
available features can be used. This includes negative items, and so
it is possible to exclude addresses from being blacklisted. For
convenience, as an additional method to whitelist addresses from being
blocked, an explicit whitelist is read in from
/etc/exim4/host_local_deny_exceptions. Entries in the whitelist override
corresponding blacklist entries.

In the blacklist, the trick is to read a line break as "or" if it
follows a positive item, and as "and" if it follows a negative item.

For example, a /etc/exim4/local_host_blacklist

.br
192.168.10.0/24
.br
!172.16.10.128/26
.br
172.16.10.0/24
.br
10.0.0.0/8

Exim just evaluates left to right (or up-down in the file listing
context), so you don't get the same kind of operator binding as in a
programming language.

.SH /etc/exim4/host_local_deny_exceptions
.I [exim host list]
contains a list of IP addresses, networks and host names whose
messages will be accepted despite the address is also listed in
/etc/exim4/local_host_blacklist, overriding a blacklisting.

.SH /etc/exim4/local_sender_blacklist
.I [exim address list]
is an optional files containing a list of envelope senders whose
messages will be denied with the error message "locally blacklisted".
This is a full exim 4 address list, and all available features can be
used. This includes negative items, and so it is possible to exclude
addresses from being blacklisted. For convenience, as an additional
method to whitelist addresses from being blocked, an explicit
whitelist is read in from /etc/exim4/sender_local_deny_exceptions. Entries
in the whitelist override corresponding blacklist entries.

In the blacklist, the trick is to read a line break as "or" if it
follows a positive item, and as "and" if it follows a negative item.

For example, a /etc/exim4/local_sender_blacklist

.br
domain1.example
.br
!local@domain2.example
.br
domain2.example
.br
domain3.example

Exim just evaluates left to right (or up-down in the file listing
context), so you don't get the same kind of operator binding as in a
programming language.

.SH /etc/exim4/sender_local_deny_exceptions
.I [exim address list]
is an optional file containing a list of envelope senders whose messages
will be accepted despite the address being also listed in
/etc/exim4/local_sender_blacklist, overriding a blacklisting.

.SH /etc/exim4/local_sender_callout
.I [exim address list]
is an optional file containing a list of envelope senders whose
messages are subject to sender verification with a callout. This is a
full exim4 address list, and all available features can be used.

.SH /etc/exim4/local_rcpt_callout
.I [exim address list]
is an optional file containing a list of envelope recipients for which
incoming messages are subject to recipient verification with a
callout. This is a full exim4 address list, and all available features
can be used.

.SH /etc/exim4/local_domain_dnsbl_whitelist
.I [exim address list]
is an optional file containing a list of envelope senders whose
messages are exempt from blacklisting via a domain-based DNSBL. This
is a full exim4 address list, and all available features can be used.
This feature is intended to be used in case of a domain-based DNSBL
being too heavy handed, for example listing entire top-level domains
for their registry policies.

.SH /etc/exim4/hubbed_hosts
.I [exim domain list]
is an optional file containing a list of route_data records which can
be used to override or augment MX information from the DNS. This is
particularly useful for mail hubs which are highest-priority MX for a
domain in the DNS but are not final destination of the messages,
passing them on to a host which is not publicly reachable, or to
temporarily fix mail routing in case of broken DNS setups.

The file should contain key-value pairs of domain pattern and route
data of the form

.br
domain: host-list options
.br
dict.ref.example:  mail\-1.ref.example:mail\-2.ref.example
.br
foo.example: internal.mail.example.com
.br
bar.example: 192.168.183.3

which will cause mail for foo.example to be sent to the host
internal.mail.example (IP address derived from A record only), and
mail to bar.example to be sent to 192.168.183.3.

See spec.txt chapter 20.3 through 20.7 for a more detailed explanation
of host list format and available options.

.SH /etc/exim4/passwd
contains account and password data for SMTP authentication when the
local exim is SMTP server and clients authenticate to the local exim.

The file should contain lines of the form

.br
username:crypted-password:clear-password

crypted-password is the crypt(3)-created hash of your password. You
can, for example, use the mkpasswd program from the whois package to
create a crypted password. It is recommended to use a modern hash
algorithm, see mkpasswd \-\-method=help. Consider not using crypt or MD5.

clear-password is only necessary if you want to offer CRAM-MD5
authentication. If you don't plan on doing so, the third column can be
omitted completely.

This file must be readable for the Debian\-exim user and should not be
readable for others. Recommended file mode is root:Debian\-exim 640.

.SH /etc/exim4/passwd.client
contains account and password data for SMTP authentication when exim
is authenticating as a client to some remote server.

The file should contain lines of the form

.br
target.mail.server.example:login-user-name:password

which will cause exim to use login-user-name and password when sending
messages to a server with the canonical host name
target.mail.server.example.  Please note that this does not configure
the mail server to send to (this is determined in Debconf), but only
creates the correlation between host name and authentication
credentials to avoid exposing passwords to the wrong host.

Please note that target.mail.server.example is currently the value
that exim can read from reverse DNS: It first follows the host name of
the target system until it finds an IP address, and then looks up the
reverse DNS for that IP address to use the outcome of this query (or
the IP address itself should the query fail) as index into
/etc/exim4/passwd.client.

This goes inevitably wrong if the host name of the mail server is a
CNAME (a DNS alias), or the reverse lookup does not fit the forward one.

Currently, you need to manually lookup all reverse DNS names for all
IP addresses that your SMTP server host name points to, for example by
using the host command.  If the SMTP smarthost alias expands to
multiple IPs, you need to have multiple lines for all the hosts.  When
your ISP changes the alias, you will need to manually fix that.

You may minimize this trouble by using a wild card entry or regular
expressions, thus reducing the risk of divulging the password to the
wrong SMTP server while reducing the number of necessary lines.  For a
deeper discussion, see the Debian BTS #244724.

password is your SMTP password in clear text. If you do not know about
your SMTP password, you can try using your POP3 password as a first
guess.

This file must be readable for the Debian\-exim user and should not be
readable for others. Recommended file mode is root:Debian\-exim 640.

.br
# example for CONFDIR/passwd.client
.br
# this will only match if the server's generic name matches exactly
.br
mail.server.example:user:password
.br
# this will deliver the password to any server
.br
*:username:password
.br
# this will deliver the password to servers whose generic name ends in
.br
# mail.server.example
.br
*.mail.server.example:user:password
.br
# this will deliver the password to servers whose generic name matches
.br
# the regular expression
.br
^smtp[0\-9]*\\.mail\\.server\\.example:user:password
.br

.SH /etc/exim4/exim.crt
contains the certificate that exim uses to initiate TLS connections.
This is public information and can be world readable.
/usr/share/doc/exim4\-base/examples/exim\-gencert can
be used to generate a private key and self-signed certificate.

.SH /etc/exim4/exim.key
contains the private key belonging to the certificate in exim.crt.
This file's contents must be kept secret and should have mode
root:Debian\-exim 640.  /usr/share/doc/exim4\-base/examples/exim\-gencert
can be used to generate a private key and self-signed certificate.

.SH BUGS
Plenty. Please report them through the Debian BTS

This manual page needs a major re-work. If somebody knows better groff
than us and has more experience in writing manual pages, any patches
would be greatly appreciated.

.SH NOTES
.SS Unresolvable items in host lists

Adding or keeping items in the abovementioned host lists which are not 
resolvable by DNS has severe consequences.

e.g. if resolving a 
.B hostname
in local_host_blacklist returns a temporary error (DNS timeout) exim
will not be able to check whether a connecting host is part of the list.
Exim will therefore return a temporary SMTP error for 
.I every
connecting host.

On the other hand if there is a permanent error in resolving a name in the
host list (the record was removed from DNS) exim behaves as if the host
does not match the list. e.g. a local_host_blacklist consisting of

notresolvable.example.com:rejectme.example.com

is equivalent to an empty one. - Exim tries to match the IP-address of the
connecting host to notresolvable.example.com, resolving this IP by DNS
fails, exim behaves as if the connecting host does not match the list. List
processing stops at this point!

Starting the list with the special pattern +ignore_unknown as a 
safeguard against this behavior is strongly recommended if hostnames are
used in hostlists.

See Exim specification Chapter 
.I Domain, host, address, and local part lists
, section
.I Behaviour when an IP address or name cannot be found.
<http://www.exim.org/exim\-html\-current/doc/html/spec_html/ch\-domain_host_address_and_local_part_lists.html>

.SH SEE ALSO
.br
.BR exim (8),
.br
.BR update\-exim4.conf(8),
.br
.BR /usr/share/doc/exim4\-base/,
.br
and for general notes and details about interaction with debconf
.BR /usr/share/doc/exim4\-base/README.Debian.gz

.SH AUTHOR
Marc Haber <mh+debian-packages@zugschlus.de> with help from Ross Boylan.