Chat Applications for Ubuntu

Quoting one of e-books

Chat Applications for Ubuntu

1. Overview:

In this section, we will discuss how to install and configure a IRC server, ircd-irc2. We will also discuss how to install and configure Jabber, an instance messaging server.

2. IRC Server:

The Ubuntu repository has many Internet Relay Chat servers. This section explains how to install and 

configure the original IRC server ircd-irc2.

2.1. Installation:

To install ircd-irc2, run the following command in the command prompt:

sudo apt-get install ircd-irc2

The configuration files are stored in /etc/ircd directory. The documents are available in /usr/

share/doc/ircd-irc2 directory.

2.2. Configuration:

The IRC settings can be done in the configuration file /etc/ircd/ircd.conf. You can set the IRC

host name in this file by editing the following line:

M:irc.localhost::Debian ircd default configuration::000A

Please make sure you add DNS aliases for the IRC host name. For instance, if you set
irc.livecipher.com as IRC host name, please make sure irc.livecipher.com is resolvable in your
Domain Name Server. The IRC host name should not be same as the host name.

The IRC admin details can be configured by editing the following line:

A:Organization, IRC dept.:Daemon <ircd@example.irc.org>:Client Server::IRCnet: 

You should add specific lines to configure the list of IRC ports to listen on, to configure Operator credentials, to configure client authentication, etc. For details, please refer to the example

configuration file

 /usr/share/doc/ircd-irc2/ircd.conf.example.gz.

The IRC banner to be displayed in the IRC client, when the user connects to the server can be set in /etc/ircd/ircd.motd file.

After making necessary changes to the configuration file, you can restart the IRC server using

following command:

sudo /etc/init.d/ircd-irc2 restart

2.3. References:

You may also be interested to take a look at other IRC servers available in Ubuntu Repository. It 

includes, ircd-ircu and ircd-hybrid.

• Refer to IRCD FAQ1 for more details about the IRC Server.

3. Jabber Instant Messaging Server

Jabber a popular instant message protocol is based on XMPP, an open standard for instant messaging, and used by many popular applications. This section covers setting up a Jabberd 2 server on a local LAN. This configuration can also be adapted to providing messaging services to users over the Internet.

3.1. Installation:

To install jabberd2, in a terminal enter:

sudo apt-get install jabberd2

3.2. Configuration :

A couple of XML configuration files will be used to configure jabberd2 for Berkeley DB user authentication. This is a very simple form of authentication. However, jabberd2 can be configured to
use LDAP, MySQL, PostgreSQL, etc for for user authentication.
First, edit /etc/jabberd2/sm.xml changing:

<id>jabber.example.com</id>

Note:
Replace jabber.example.com with the hostname, or other id, of your server.

Now in the <storage> section change the <driver> to:

<driver>db</driver>

Next, edit /etc/jabberd2/c2s.xml in the <local> section change:

<id>jabber.example.com</id>

And in the <authreg> section adjust the <module> section to:

<module>db</module>

Finally, restart jabberd2 to enable the new settings:

sudo /etc/init.d/jabberd2 restart 

You should now be able to connect to the server using a Jabber client like Pidgin for example.

Note:

The advantage of using Berkeley DB for user data is that after being configured no additional maintenance is required. If you need more control over user accounts and credentials another authentication method is recommended.

3.3. References:

• The Jabberd2 Web Site2 contains more details on configuring Jabberd2.
• For more authentication options see the Jabberd2 Install Guide3.
• Also, the Setting Up Jabber Server Ubuntu Wiki4 page has more information.

See you in the next lesson

Mr.Mohamed samir™

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Mail Filtering for Ubuntu

Quoting one of e-books

Mail Filtering:

One of the largest issues with email today is the problem of Unsolicited Bulk Email (UBE). Also known as SPAM, such messages may also carry viruses and other forms of malware. According to some reports these messages make up the bulk of all email traffic on the Internet.

This section will cover integrating Amavisd-new, Spamassassin, and ClamAV with the Postfix Mail Transport Agent (MTA). Postfix can also check email validity by passing it through external content

filters. These filters can sometimes determine if a message is spam without needing to process it with more resource intensive applications. Two common filters are opendkim and python-policyd-spf.

• Amavisd-new is a wrapper program that can call any number of content filtering programs for spam

detection, antivirus, etc.

• Spamassassin uses a variety of mechanisms to filter email based on the message content.

• ClamAV is an open source antivirus application.

• opendkim implements a Sendmail Mail Filter (Milter) for the DomainKeys Identified Mail (DKIM)

standard.

• python-policyd-spf enables Sender Policy Framework (SPF) checking with Postfix.

This is how the pieces fit together:

• An email message is accepted by Postfix.

• The message is passed through any external filters opendkim and python-policyd-spf in this case.

• Amavisd-new then processes the message.

• ClamAV is used to scan the message. If the message contains a virus Postfix will reject the

message.

• Clean messages will then be analyzed by Spamassassin to find out if the message is spam.

Spamassassin will then add X-Header lines allowing Amavisd-new to further manipulate the message. 

For example, if a message has a Spam score of over fifty the message could be automatically dropped from the queue without the recipient ever having to be bothered. Another, way to handle flagged messages is to deliver them to the Mail User Agent (MUA) allowing the user to deal with the message as they see fit.

Installation:

To install the rest of the applications enter the following from a terminal prompt:

sudo apt-get install amavisd-new spamassassin clamav-daemon

sudo apt-get install opendkim postfix-policyd-spf-python

There are some optional packages that integrate with Spamassassin for better spam detection:

sudo apt-get install pyzor razor

Along with the main filtering applications compression utilities are needed to process some email attachments:

sudo apt-get install arj cabextract cpio lha nomarch pax rar unrar unzip zip

Note:

If some packages are not found, check that the multiverse repository is enabled in /etc/apt/ 

sources.list

If you make changes to the file, be sure to run sudo apt-get update before trying to install again.

Configuration:

Now configure everything to work together and filter email.

ClamAV:

The default behaviour of ClamAV will fit our needs. For more ClamAV configuration options, check the configuration files in /etc/clamav.

Add the clamav user to the amavis group in order for Amavisd-new to have the appropriate access to scan files:

sudo adduser clamav amavis

sudo adduser amavis clamav

Spamassassin: 

Spamassassin automatically detects optional components and will use them if they are present. This means that there is no need to configure pyzor and razor.

Edit /etc/default/spamassassin to activate the Spamassassin daemon. Change ENABLED=0 to:

ENABLED=1

Now start the daemon:

sudo /etc/init.d/spamassassin start

Amavisd-new:

First activate spam and antivirus detection in Amavisd-new by editing

/etc/amavis/conf.d/15-content_filter_mode:

use strict;

# You can modify this file to re-enable SPAM checking through spamassassin

# and to re-enable antivirus checking.

#

# Default antivirus checking mode

# Uncomment the two lines below to enable it

#

@bypass_virus_checks_maps = (

\%bypass_virus_checks, \@bypass_virus_checks_acl, \$bypass_virus_checks_re);

#

# Default SPAM checking mode

# Uncomment the two lines below to enable it

#

@bypass_spam_checks_maps = (

\%bypass_spam_checks, \@bypass_spam_checks_acl, \$bypass_spam_checks_re);

1; # insure a defined return

Bouncing spam can be a bad idea as the return address is often faked. Consider editing /etc/amavis/ conf.d/20-debian_defaults to set $final_spam_destiny to D_DISCARD rather than D_BOUNCE,

as follows:

$final_spam_destiny = D_DISCARD;

Additionally, you may want to adjust the following options to flag more messages as spam:

$sa_tag_level_deflt = -999; # add spam info headers if at, or above that level

$sa_tag2_level_deflt = 6.0; # add 'spam detected' headers at that level

$sa_kill_level_deflt = 21.0; # triggers spam evasive actions

$sa_dsn_cutoff_level = 4; # spam level beyond which a DSN is not sent

If the server's hostname is different from the domain's MX record you may need to manually set the $myhostname option. Also, if the server receives mail for multiple domains the @local_domains_acl

option will need to be customized. Edit the /etc/amavis/conf.d/50-user file:

$myhostname = 'mail.example.com';

@local_domains_acl = ( "example.com", "example.org" );

If you want to cover multiple domains you can use the following in the/etc/amavis/conf.d/50-user

@local_domains_acl = qw(.);

After configuration Amavisd-new needs to be restarted:

sudo /etc/init.d/amavis restart

DKIM Whitelist:

Amavisd-new can be configured to automatically Whitelist addresses from domains with

valid Domain Keys. There are some pre-configured domains in the /etc/amavis/conf.d/40-

policy_banks.

There are multiple ways to configure the Whitelist for a domain:

• 'example.com' => 'WHITELIST',: will whitelist any address from the "example.com" domain.

• '.example.com' => 'WHITELIST',: will whitelist any address from any subdomains of

"example.com" that have a valid signature.

• '.example.com/@example.com' => 'WHITELIST',: will whitelist subdomains of "example.com" that

use the signature of example.com the parent domain.

• './@example.com' => 'WHITELIST',: adds addresses that have a valid signature from

"example.com". This is usually used for discussion groups that sign their messages.

A domain can also have multiple Whitelist configurations. After editing the file, restart amavisd-new:

sudo /etc/init.d/amavis restart

Note:

In this context, once a domain has been added to the Whitelist the message will not receive 

any anti-virus or spam filtering. This may or may not be the intended behavior you wish for 

a domain.

Postfix

For Postfix integration, enter the following from a terminal prompt:

sudo postconf -e 'content_filter = smtp-amavis:[127.0.0.1]:10024'

Next edit /etc/postfix/master.cf and add the following to the end of the file:

smtp     -     amavis      unix      -      -      -      -      2      smtp

          -o smtp_data_done_timeout=1200

         -o smtp_send_xforward_command=yes

         -o disable_dns_lookups=yes

         -o max_use=20

127.0.0.1:10025 inet n - - - - smtpd

         -o content_filter=

         -o local_recipient_maps=

         -o relay_recipient_maps=

         -o smtpd_restriction_classes=

         -o smtpd_delay_reject=no

         -o smtpd_client_restrictions=permit_mynetworks,reject

         -o smtpd_helo_restrictions=

         -o smtpd_sender_restrictions=

         -o smtpd_recipient_restrictions=permit_mynetworks,reject

         -o smtpd_data_restrictions=reject_unauth_pipelining

         -o smtpd_end_of_data_restrictions=

         -o mynetworks=127.0.0.0/8

         -o smtpd_error_sleep_time=0

         -o smtpd_soft_error_limit=1001

         -o smtpd_hard_error_limit=1000

         -o smtpd_client_connection_count_limit=0

         -o smtpd_client_connection_rate_limit=0

         -o receive_override_options=no_header_body_checks,no_unknown_recipient_checks

Also add the following two lines immediately below the "pickup" transport service:

         -o content_filter=

         -o receive_override_options=no_header_body_checks

This will prevent messages that are generated to report on spam from being classified as spam.

Now restart Postfix:

sudo /etc/init.d/postfix restart

Content filtering with spam and virus detection is now enabled.

Amavisd-new and Spamassassin:

When integrating Amavisd-new with Spamassassin, if you choose to disable the bayes filtering by editing /etc/spamassassin/local.cf and use cron to update the nightly rules, the result can cause a

situation where a large amount of error messages are sent to the amavis user via the amavisd-new cron

job.

There are several ways to handle this situation:

• Configure your MDA to filter messages you do not wish to see.

• Change /usr/sbin/amavisd-new-cronjob to check for use_bayes 0. For example, edit /usr/sbin/ amavisd-new-cronjob and add the following to the top before the test statements:

egrep -q "^[ \t]*use_bayes[ \t]*0" /etc/spamassassin/local.cf && exit 0

Testing:

First, test that the Amavisd-new SMTP is listening:

telnet localhost 10024

Trying 127.0.0.1...

Connected to localhost.

Escape character is '^]'.

220 [127.0.0.1] ESMTP amavisd-new service ready

^]

In the Header of messages that go through the content filter you should see:

X-Spam-Level:

X-Virus-Scanned: Debian amavisd-new at example.com

X-Spam-Status: No, hits=-2.3 tagged_above=-1000.0 required=5.0 tests=AWL, BAYES_00

X-Spam-Level:

Note:

Your output will vary, but the important thing is that there are X-Virus-Scanned and XSpam-Status entries.

Troubleshooting:

The best way to figure out why something is going wrong is to check the log files.

• For instructions on Postfix logging see the Section 1.7, “Troubleshooting” [p. 239] section.

• Amavisd-new uses Syslog to send messages to /var/log/mail.log. The amount of detail can be increased by adding the $log_level option to /etc/amavis/conf.d/50-user, and setting the value

from 1 to 5.

$log_level = 2;

Note:

When the Amavisd-new log output is increased Spamassassin log output is also increased.

• The ClamAV log level can be increased by editing /etc/clamav/clamd.conf and setting the

following option:

LogVerbose true

By default ClamAV will send log messages to /var/log/clamav/clamav.log.

Note:

After changing an applications log settings remember to restart the service for the new settings to take affect. Also, once the issue you are troubleshooting is resolved it is a good idea to change the log settings back to normal.

See you in the next lesson

Mr.Mohamed samir™

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Mailman for Ubuntu

Quoting one of e-books

4.Mailman

Mailman is an open source program for managing electronic mail discussions and e-newsletter lists.

Many open source mailing lists (including all the Ubuntu mailing lists17) use Mailman as their mailing list software. It is powerful and easy to install and maintain.

4.1. Installation

Mailman provides a web interface for the administrators and users, using an external mail server to send and receive emails. It works perfectly with the following mail servers:

• Postfix

• Exim

• Sendmail

• Qmail

We will see how to install and configure Mailman with, the Apache web server, and either the Postfix or Exim mail server. If you wish to install Mailman with a different mail server, please refer to the

references section.

Note:

You only need to install one mail server and Postfix is the default Ubuntu Mail Transfer 

Agent.

Once exim4 is installed, the configuration files are stored in the /etc/exim4 directory. In Ubuntu, by default, the exim4 configuration files are split across different files. You can change this behavior by changing the following variable in the /etc/exim4/update-exim4.conf file:

dc_use_split_config='true'

Mailman:

To install Mailman, run following command at a terminal prompt:

sudo apt-get install mailman

It copies the installation files in /var/lib/mailman directory. It installs the CGI scripts in /usr/lib/cgibin/ mailman directory. It creates list linux user. It creates the list linux group. The mailman process will be owned by this user.

Configuration

This section assumes you have successfully installed mailman, apache2, and postfix or exim4. Now you just need to configure them.

Apache2

An example Apache configuration file comes with Mailman and is placed in /etc/mailman/ apache.conf. In order for Apache to use the config file it needs to be copied to /etc/apache2/ sites-available:

sudo cp /etc/mailman/apache.conf /etc/apache2/sites-available/mailman.conf

This will setup a new Apache VirtualHost for the Mailman administration site. Now enable the new configuration and restart Apache:

sudo a2ensite mailman.conf

sudo service apache2 restart

Mailman uses apache2 to render its CGI scripts. The mailman CGI scripts are installed in the /usr/lib/ cgi-bin/mailman directory. So, the mailman url will be http://hostname/cgi-bin/mailman/. You can

make changes to the /etc/apache2/sites-available/mailman.conf file if you wish to change this behavior.

Postfix

For Postfix integration, we will associate the domain lists.example.com with the mailing lists. Please replace lists.example.com with the domain of your choosing.

You can use the postconf command to add the necessary configuration to /etc/postfix/main.cf:

sudo postconf -e 'relay_domains = lists.example.com'

sudo postconf -e 'transport_maps = hash:/etc/postfix/transport'

sudo postconf -e 'mailman_destination_recipient_limit = 1'

In /etc/postfix/master.cf double check that you have the following transport:

mailman    unix 

   -     n    n    -  -   pipe

flags=FR user=list argv=/usr/lib/mailman/bin/postfix-to- ailman.py

${nexthop} ${user}

It calls the postfix-to-mailman.py script when a mail is delivered to a list.

Associate the domain lists.example.com to the Mailman transport with the transport map. Edit the file

/etc/postfix/transport:

lists.example.com   mailman:

Now have Postfix build the transport map by entering the following from a terminal prompt:

sudo postmap -v /etc/postfix/transport

Then restart Postfix to enable the new configurations:

sudo /etc/init.d/postfix restart

Exim4

Once Exim4 is installed, you can start the Exim server using the following command from a terminal prompt:

sudo /etc/init.d/exim4 start

In order to make mailman work with Exim4, you need to configure Exim4. As mentioned earlier, by default, Exim4 uses multiple configuration files of different types. For details, please refer to

the Exim18 web site. To run mailman, we should add new a configuration file to the following configuration types:

• Main

• Transport

• Router

Exim creates a master configuration file by sorting all these mini configuration files. So, the order of these configuration files is very important.

Main

All the configuration files belonging to the main type are stored in the /etc/exim4/conf.d/main/ directory. You can add the following content to a new file, named 04_exim4-config_mailman:

# start

# Home dir for your Mailman installation -- aka Mailman's prefix

# directory.

# On Ubuntu this should be "/var/lib/mailman"

# This is normally the same as ~mailman

MM_HOME=/var/lib/mailman

#

# User and group for Mailman, should match your --with-mail-gid

# switch to Mailman's configure script. Value is normally "mailman"

MM_UID=list

MM_GID=list

#

# Domains that your lists are in - colon separated list

# you may wish to add these into local_domains as well

domainlist mm_domains=hostname.com

#

# -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

#

# These values are derived from the ones above and should not need

# editing unless you have munged your mailman installation

#

# The path of the Mailman mail wrapper script

MM_WRAP=MM_HOME/mail/mailman

#

# The path of the list config file (used as a required file when

# verifying list addresses)

MM_LISTCHK=MM_HOME/lists/${lc::$local_part}/config.pck

# end

Transport

All the configuration files belonging to transport type are stored in the /etc/exim4/conf.d/ 

transport/ directory. You can add the following content to a new file named 40_exim4- 

config_mailman:

mailman_transport:

 driver = pipe

 command = MM_WRAP \

             '${if def:local_part_suffix \

                {${sg{$local_part_suffix}{-(\\w+)(\\+.*)?}{\$1}}} \

                {post}}' \

             $local_part

current_directory = MM_HOME

home_directory = MM_HOME

user = MM_UID

group = MM_GID

Router

All the configuration files belonging to router type are stored in the /etc/exim4/conf.d/router/ 

directory. You can add the following content in to a new file named 101_exim4-config_mailman:

mailman_router:

driver = accept

require_files = MM_HOME/lists/$local_part/config.pck

local_part_suffix_optional

local_part_suffix = -bounces : -bounces+* : \

-confirm+* : -join : -leave : \

-owner : -request : -admin

transport = mailman_transport

Stop:

The order of main and transport configuration files can be in any order. But, the order of router configuration files must be the same. This particular file must appear before the 200_exim4-config_primary file. These two configuration files contain same  ype

of information. The first file takes the precedence. For more details, please refer to the references section.

Mailman

Once mailman is installed, you can run it using the following command:

sudo /etc/init.d/mailman start

Once mailman is installed, you should create the default mailing list. Run the following command to

create the mailing list:

sudo /usr/sbin/newlist mailman

Enter the email address of the person running the list: bhuvan at ubuntu.com

Initial mailman password:

To finish creating your mailing list, you must edit your /etc/aliases (or equivalent) file by adding the following lines, and possibly running the `newaliases' program:

## mailman mailing list

mailman:                             "|/var/lib/mailman/mail/mailman post mailman"

mailman-admin:                  "|/var/lib/mailman/mail/mailman admin mailman"

mailman-bounces:              "|/var/lib/mailman/mail/mailman bounces mailman"

mailman-confirm:               "|/var/lib/mailman/mail/mailman confirm mailman"

mailman-join:                    "|/var/lib/mailman/mail/mailman join mailman"

mailman-leave:                 "|/var/lib/mailman/mail/mailman leave mailman"

mailman-owner:              "|/var/lib/mailman/mail/mailman owner mailman"

mailman-request:            "|/var/lib/mailman/mail/mailman request mailman"

mailman-subscribe:        "|/var/lib/mailman/mail/mailman subscribe mailman"

mailman-unsubscribe:    "|/var/lib/mailman/mail/mailman unsubscribe mailman"

Hit enter to notify mailman owner...

#

We have configured either Postfix or Exim4 to recognize all emails from mailman. So, it is not mandatory to make any new entries in /etc/aliases. If you have made any changes to the configuration files, please ensure that you restart those services before continuing to next section.

Note:

The Exim4 does not use the above aliases to forward mails to Mailman, as it uses a discover approach. To suppress the aliases while creating the list, you can add MTA=None line in Mailman configuration file, /etc/mailman/mm_cfg.py.

Administration

We assume you have a default installation. The mailman cgi scripts are still in the /usr/lib/cgi-bin/

mailman/ directory. Mailman provides a web based administration facility. To access this page, point your browser to the following url:

http://hostname/cgi-bin/mailman/admin

The default mailing list, mailman, will appear in this screen. If you click the mailing list name, it will ask for your authentication password. If you enter the correct password, you will be able to change administrative settings of this mailing list. You can create a new mailing list using the command line utility (/usr/sbin/newlist). Alternatively, you can create a new mailing list using the web interface.

Users:

Mailman provides a web based interface for users. To access this page, point your browser to the following url:

http://hostname/cgi-bin/mailman/listinfo

The default mailing list, mailman, will appear in this screen. If you click the mailing list name, it will display the subscription form. You can enter your email address, name (optional), and password to

subscribe. An email invitation will be sent to you. You can follow the instructions in the email to subscribe.

See you in the next lesson

Mr.Mohamed samir™

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Dovecot Server for ubuntu

Dovecot Server

Quoting one of e-books

3.Dovecot Server :


Dovecot is a Mail Delivery Agent, written with security primarily in mind. It supports the major mailbox formats: mbox or Maildir. This section explain how to set it up as an imap or pop3 server.


3.1. Installation:
To install dovecot, run the following command in the command prompt:

sudo apt-get install dovecot-imapd dovecot-pop3d

3.2. Configuration:

To configure dovecot, you can edit the file /etc/dovecot/dovecot.conf. You can choose the protocol you use. It could be pop3, pop3s (pop3 secure), imap and imaps (imap secure). A description of these protocols is beyond the scope of this guide. For further information, refer to the Wikipedia articles on POP312 and IMAP13


IMAPS and POP3S are more secure that the simple IMAP and POP3 because they use SSL encryption to connect. Once you have chosen the protocol, amend the following line in the file 

/etc/dovecot/dovecot.conf:

protocols = pop3 pop3s imap imaps


Next, choose the mailbox you would like to use. Dovecot supports maildir and mbox formats. These are the most commonly used mailbox formats. They both have their own benefits and are discussed on the Dovecot web site14.


Once you have chosen your mailbox type, edit the file /etc/dovecot/dovecot.conf and change the following line:


mail_location = maildir:~/Maildir # (for maildir)
or
mail_location = mbox:~/mail:INBOX=/var/spool/mail/%u # (for mbox)




Note:

You should configure your Mail Transport Agent (MTA) to transfer the incoming mail to this type of mailbox if it is different from the one you have configured.


Once you have configured dovecot, restart the dovecot daemon in order to test your setup:

sudo /etc/init.d/dovecot restart

If you have enabled imap, or pop3, you can also try to log in with the commands telnet localhost pop3 or telnet localhost imap2. If you see something like the following, the installation has been

successful:

bhuvan@rainbow:~$ telnet localhost pop3
Trying 127.0.0.1...
Connected to localhost.localdomain.
Escape character is '^]'.
+OK Dovecot ready

3.3. Dovecot SSL Configuration:


To configure dovecot to use SSL, you can edit the file /etc/dovecot/dovecot.conf and amend 

following lines:

ssl_cert_file = /etc/ssl/certs/ssl-cert-snakeoil.pem

ssl_key_file = /etc/ssl/private/ssl-cert-snakeoil.key

ssl_disable = no

disable_plaintext_auth = no

You can get the SSL certificate from a Certificate Issuing Authority or you can create self signed SSL certificate. The latter is a good option for email, because SMTP clients rarely complain about "selfsigned certificates". Please refer to Section 5, “Certificates” [p. 171] for details about how to create self signed SSL certificate. Once you create the certificate, you will have a key file and a certificate file. Please copy them to the location pointed in the /etc/dovecot/dovecot.conf configuration file.

3.4. Firewall Configuration for an Email Server:


To access your mail server from another computer, you must configure your firewall to allow connections to the server on the necessary ports.


• IMAP - 143
• IMAPS - 993
• POP3 - 110
• POP3S - 995


3.5. References:
• See the Dovecot website15 for more information.
• Also, the Dovecot Ubuntu Wiki16 page has more details.

See you in the next lesson

Mr.Mohamed samir™

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Exim4 for ubuntu

Quoting one of e-books

Exim4

2. Exim4

Exim4 is another Message Transfer Agent (MTA) developed at the University of Cambridge for use 

on Unix systems connected to the Internet. Exim can be installed in place of sendmail, although the 

configuration of exim is quite different to that of sendmail.

2.1. Installation:

To install exim4, run the following command:

sudo apt-get install exim4

2.2. Configuration:

To configure Exim4, run the following command:

sudo dpkg-reconfigure exim4-config

The user interface will be displayed. The user interface lets you configure many parameters. For example, In Exim4 the configuration files are split among multiple files. If you wish to have them in one file you can configure accordingly in this user interface.

All the parameters you configure in the user interface are stored in /etc/exim4/update-exim4.conf file. If you wish to re-configure, either you re-run the configuration wizard or manually edit this file using your favorite editor. Once you configure, you can run the following command to generate the master configuration file:

sudo update-exim4.conf

The master configuration file, is generated and it is stored in /var/lib/exim4/config.autogenerated.

Stpo:

At any time, you should not edit the master configuration file, /var/lib/exim4/

config.autogenerated manually. It is updated automatically every time you run update-exim4.conf

You can run the following command to start Exim4 daemon.

sudo /etc/init.d/exim4 start

2.3. SMTP Authentication:

This section covers configuring Exim4 to use SMTP-AUTH with TLS and SASL.

The first step is to create a certificate for use with TLS. Enter the following into a terminal prompt:

sudo /usr/share/doc/exim4-base/examples/exim-gencert

Now Exim4 needs to be configured for TLS by editing /etc/exim4/conf.d/main/03_exim4- config_tlsoptions add the following:

MAIN_TLS_ENABLE = yes



Next you need to configure Exim4 to use the saslauthd for authentication. Edit /etc/exim4/conf.d/auth/30_exim4-config_examples and uncomment the plain_saslauthd_server and
login_saslauthd_server sections:


plain_saslauthd_server:
    driver = plaintext
   public_name = PLAIN
   server_condition = ${if saslauthd{{$auth2}{$auth3}}{1}{0}}
   server_set_id = $auth2
   server_prompts = :
   .ifndef AUTH_SERVER_ALLOW_NOTLS_PASSWORDS
   server_advertise_condition = ${if eq{$tls_cipher}{}{}{*}}
   .endif
#
  login_saslauthd_server:
   driver = plaintext
   public_name = LOGIN
   server_prompts = "Username:: : Password::"
   # don't send system passwords over unencrypted connections
   server_condition = ${if saslauthd{{$auth1}{$auth2}}{1}{0}}
   server_set_id = $auth1
   .ifndef AUTH_SERVER_ALLOW_NOTLS_PASSWORDS
   server_advertise_condition = ${if eq{$tls_cipher}{}{}{*}}
   .endif

Additionally, in order for outside mail client to be able to connect to new exim server, new user needs
to be added into exim by using the following commands.



sudo /usr/share/doc/exim4/examples/exim-adduser

Users should protect the new exim password files with the following commands.


sudo chown root:Debian-exim /etc/exim4/passwd
sudo chmod 640 /etc/exim4/passwd



Finally, update the Exim4 configuration and restart the service:

sudo update-exim4.conf
sudo /etc/init.d/exim4 restart

2.4. Configuring SASL:



This section provides details on configuring the saslauthd to provide authentication for Exim4.

The first step is to install the sasl2-bin package. From a terminal prompt enter the following:

sudo apt-get install sasl2-bin

To configure saslauthd edit the /etc/default/saslauthd configuration file and set START=no to:

START=yes

Next the Debian-exim user needs to be part of the sasl group in order for Exim4 to use the saslauthd service:

sudo adduser Debian-exim sasl

Now start the saslauthd service:

sudo /etc/init.d/saslauthd start


Exim4 is now configured with SMTP-AUTH using TLS and SASL authentication.

2.5. References:



• See exim.org9 for more information.
• There is also an Exim4 Book10 available.
• Another resource is the Exim4 Ubuntu Wiki 11 page.

See you in the next lesson

Mr.Mohamed samir™

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