Quelltext der Seite How to Install Dovecot IMAP Mail Server and Fetchmail on Debian

This article describes how to build a IMAP mail server based on Dovecot with Debian as operating system based on following versions: 

* Debian 10.x
* Dovecot 2.3.4.x
* Apache 2.4
* Roundcube 1.4.8

In the configuration described below Dovecot only serves as a IMAP server for emails. 

Emails will be fetched from remote IMAP servers via Fetchmail.

SMTP will not be provided by this server. Instead for sending emails external SMTP servers at your mail provider will be used. Exim4 will be configured to forward mails to such an external smarthost. All clients will connect directly to that external SMTP server. This simplifies installation, configuration and operation one does not have to care for a SMTP mail server.

Dovecot and Debian will be configured to use Maildir. 

== Exim4 ==

=== Installation ===

 # apt-get install exim4

=== Configure an External Smarthost for SMTP ===
 
 # dpkg-reconfigure exim4-config

Werte können folgendermaßen gefüllt werden:
{| class="wikitable"
!Einstellung
!Beispielwerte
|-
|Generelle E-Mail-Einstellungen
|Versand über Sendezentrale (Smarthost); Empfang über SMTP oder Fetchmail oder

Versand über Sendezentrale (Smarthost); Keine lokale E-Mail-Zustellung
|-
|E-Mail-Name des Systems
|mail.domain.tld
|-
|IP-Adressen, an denen eingehende SMTP-Verbindungen erwartet werden
|127.0.0.1;::1
|-
|Weitere Ziele, für die die E-Mails angenommen werden sollen
|Feld leer lassen. -> Optional hier die Maildomäne eingeben?
|-
|Rechner, für die E-Mails weitergeleitet werden (Relay)
|Leer lassen, damit der Server nicht als Relay verwendet wird.
|-
|IP-Adresse oder Rechnername der Sendezentrale für ausgehende E-Mails
|SMTP Server des Externen Providers
|-
|Lokalen E-Mail-Namen in ausgehenden E-Mails verbergen
|Nein
|-
|Versandart bei lokaler E-Mail-Zustellung
|Maildir-Format im Home-Verzeichnis
|-
|Einstellungen auf kleine Dateien aufteilen (Splitkonfiguration)
|Nein
|}
Wenn Einstellungen nicht auf kleine Dateien aufgeteilt werden, werden die Einstellungen aus <code>/etc/exim4/*.conf</code> -Dateien verwendet.

Passwörter für SMTP-authentifizierung eingeben in:
 nano /etc/exim4/passwd.client

Format für Passwörter
 <smarthostserver>:<username_für_anmeldung>:<passwort>

=== Send a test mail ===

 echo This is a Text body | mail -s "<subject>" <recipient>


== Reconfigure Debian for Maildir ==

=== Show Mail Status on Login ===

In order to get notifications about mail status when logging in the following changes have to be done:

Anpassungen <code>/etc/pam.d/login</code>
  # in /etc/login.defs to make sure that removing a user 
  # also removes the user's mail spool file.
  # See comments in /etc/login.defs
 -session    optional   pam_mail.so standard
 +session    optional   pam_mail.so dir=~/Maildir standard

Anpassungen <code>/etc/pam.d/sshd</code>
  # Print the status of the user's mailbox upon successful login.
 -session    optional     pam_mail.so standard noenv # [1]
 +session    optional     pam_mail.so dir=~/Maildir standard # [1]

Anpassungen <code>/etc/pam.d/su</code>
  # "nopen" stands to avoid reporting new mail when su'ing to another user
 -session    optional   pam_mail.so nopen
 +session    optional   pam_mail.so dir=~/Maildir nopen

=== Reconfigure Mutt ===

Reconfigure Mutt to Maildir:

Create new file <code>/etc/Muttrc.d/my-mutt.rc</code>.

 set mbox_type=Maildir
 set folder = '~/Maildir'
 set record="+.Sent";
 set postponed="+.Drafts"

For more details see [[Mutt (Debian)|Mutt]]

== Install Roundcube ==

=== Install Apache ===

 apt-get install apache2

=== Add VirtualHost to Apache ===

Create a new configuration file <code>/etc/apache2/sites-available/roundcube.conf</code>:

 <VirtualHost *:80>
   DocumentRoot /var/www/roundcube
   ServerName roundcube.yourdomain.com
 
   RewriteEngine on
   RewriteCond %{SERVER_NAME} =roundcube.yourdomain.com
   RewriteRule ^ https://%{SERVER_NAME}%{REQUEST_URI} [END,NE,R=permanent]
 </VirtualHost>
 
 <Directory /var/www/roundcube>
   AllowOverride All
 </Directory>

Enable VirtualHost in Apache:

 a2ensite roundcube
 systemctl reload roundcube

=== Add Let's Encrypt to VirtualHost ===

Install certbot if not already installed:

 apt-get install certbot

Enable Let's Entrypt for new VirtualHost:

 certbot --apache 

Follow instructions on screen.

For more details see [[Let's_encrypt]]

=== Add PHP Modules ===

 apt-get install php-ldap

Enable Module Expires (needed for Roundcube):

 a2enmod expires

=== Download Roundcube ===

Download to /var/www

 wget https://github.com/roundcube/roundcubemail/releases/download/1.4.x/roundcubemail-1.4.x-complete.tar.gz

Extract with

 tar xvf roundcubemail-1.4.x-complete.tar.gz

Rename folder roundcubemail-1.4.x to roundcube.

Follow INSTALL text file.

=== Create Database ===

Login to MariaDB as root and create database with following commands:

 CREATE DATABASE roundcube CHARACTER SET utf8 COLLATE utf8_general_ci;
 CREATE USER roundcube@localhost IDENTIFIED BY '<enter-password-here>';
 GRANT ALL PRIVILEGES ON roundcube.* TO roundcube@localhost;

Create initial database tables with:

 mysql -u -p roundcube < /var/www/roundcube/SQL/mysql.initial.sql

=== Installation ===

Open URL: https://roundcube.yourserver.com/installer

Follow instructions.

Values for <code>config.inc.php</code>:

 $config['default_host'] = 'ssl://roundcube.yourdomain.com';
 $config['default_port'] = 993;

=== Identity SMTP Plugin ===

This plugin enables to use different SMTP servers based on a given identity.

Source: https://github.com/deflomu/Roundcube-SMTP-per-Identity-Plugin

 cd /var/www/roundcube/plugins
 git clone git://github.com/deflomu/Roundcube-SMTP-per-Identity-Plugin identity_smtp

Alter configuration file <code>/var/www/roundcube/config/config.inc.php</code>.

Add '''identity_smtp''':

 $config['plugins'] = array( 
   ...,
   'identity_smtp',
 );

Identity SMTP-Plugin requires a default SMTP server in the Roundcube configuration file:

 $config['smtp_server'] = 'ssl://localhost';

=== Cronjob for Database Cleaning ===

Create a new file <code>/etc/cron.d/roundcube</code>:

 # /etc/cron.d/roundcube: Housekeeping cronjob for Roundcube
 #
 # m h dom mon dow user     command
 13  2  *   *   *  www-data /var/www/roundcube/bin/cleandb.sh

=== Reconfigure PHP ===

The maximum size of email attachments and other file uploads is controlled by
PHP settings: upload_max_filesize and post_max_size. Read more about PHP
settings at https://github.com/roundcube/roundcubemail/wiki/Installation#php-configuration.

Create new file <code>/etc/php/x.x/fpm/conf.d/roundcube.ini</code>:

 [PHP]
 upload_max_filesize = 50M
 post_max_size = 50M

=== Security ===

Disable installer in <code>config.inc.php</code> by adding following line:

 $config['enable_installer'] = false;

Move root of vhost to public_html:

 <VirtualHost *:80>
   DocumentRoot /var/www/roundcube/public_html 
   ...
 </VirtualHost>

Do the same in the vhost file for SSL created by certbot.

== Install Dovecot Server ==

=== Install ===

 apt-get install dovecot-imapd

=== Configure ===

Create configuration file <code>/etc/dovecot/conf.d/99-my-dovecot.conf</code>:

 disable_plaintext_auth = yes
 mail_location = maildir:~/Maildir
 ssl = required
 ssl_cert = </etc/letsencrypt/live/host.yourserver.tld/fullchain.pem
 ssl_key = </etc/letsencrypt/live/host.yourserver.tld/privkey.pem
 
 namespace inbox {
   mailbox Drafts {
     special_use = \Drafts
   }
   mailbox Junk {
     special_use = \Junk
   }
   mailbox Trash {
     special_use = \Trash
   }
   mailbox Sent {
     special_use = \Sent
   }
   mailbox Archive {
     special_use = \Archive
   }
 }

For details see [[Dovecot-IMAP-Server_installieren_(Debian)]]

=== Test ===

See [[Dovecot-IMAP-Server_installieren_(Debian)#Zugriff_testen]]

== IMAP Download via Fetchmail ==

For more details see [[Fetchmail (Debian)]]

=== Install Fetchmail ===

 apt-get install fetchmail

=== Configure IMAP IDLE ===

Source: http://fnxweb.com/blog/2012/07/14/using-multiple-fetchmail-instances-for-instant-gratification/

The description above is altered to match Debian folders and security.

Files:

http://www.fnxweb.com/data/fetchmail-service --> Save as fetchmail-imap-idle at '''/usr/local/bin'''

http://www.fnxweb.com/data/fetchmail.service --> Save as fetchmail-imap-idle.service at '''/usr/local/bin'''

Add execute permissions:

 chmod +x /usr/local/bin/fetchmail-imap-idle

Create symbolic link to fetchmail-imap-idle.service in '''/etc/systemd/system''':

 ln -s /usr/local/bin/fetchmail-imap-idle.service /etc/systemd/system/fetchmail-imap-idle.service
 
Place config files at: '''/etc/fetchmail.conf.d/*.conf'''

Each config file should contain only one IMAP connection.

Example ''/etc/fetchmail.conf.d/my-imap-account1-inbox.conf''

 poll host.domain.tld protocol IMAP
      user "<username@host.domain.tld>" with pass "<password>" is "<username@localhost>" here
      idle
      ssl

Avoid parameter '''fetchall''' in IMAP IDLE config files as this leads to somewhat intransparent behavior of the local dovecot LDA and emails don't appear at once rather than somewhat delayed. 

Fix: Try to send another mail to remote mailbox. After that it seems that all missing mails appear magically in Dovecot mailbox.

Alter '''/usr/local/bin/fetchmail-imap-idle''':

Change lines 10 and 11 as follows:

 fetchmailuser=fetchmail
 fetchmailgroup=nogroup

Alter paths and executable names in ''/etc/systemd/system/fetchmail.service'' as follows:

 [Unit]
 Description=A remote mail retrieval and forwarding utility
 After=network-online.target sendmail.service 
 
 [Service]
 ExecStart=/usr/local/bin/fetchmail-imap-idle start
 ExecReload=/usr/local/bin/fetchmail-imap-idle restart
 ExecStop=/usr/local/bin/fetchmail-imap-idle stop
 Type=forking
 GuessMainPID=no
 
 [Install]
 WantedBy=multi-user.target

Activate service as follows:

 systemctl enable fetchmail-imap-idle
 systemctl start fetchmail-imap-idle

=== Configure Periodical Downloads via Cronjob ===

Create <code>~/.fetchmailrc</code> which downloads all mails from INBOX folder at the specified host:

 poll host.domain.tld protocol IMAP
      user "<username@host.domain.tld>" is "<username@localhost>" here
      ssl fetchall

...as well as other folders via MDA...

 poll host.domain.tld protocol IMAP
      user "<username@host.domain.tld>" is "<username@localhost>" here
      folder Sent
      ssl fetchall
      mda "/usr/lib/dovecot/deliver -d <username@localhost> -m Sent"

Create password file <code>~/.netrc</code>:

 machine <host1.domain.tld>
 login <username@host1.domain.tld>
 password <pass>
 
 machine <host2.domain.tld>
 login <username@host2.domain.tld>
 password <pass>

Create user specific cronjob with <code>crontab -e</code> and add following line:

 */3 * * * * fetchmail

=== Remove Unseen Flag in Sent Folder ===

When using Fetchmail to download Sent folder every downloaded mail will be flagged as unseen.

In order to mark them seen create following cronjob with <code>crontab -e</code>.

 */3 * * * * doveadm flags add -u <username@localhost> '\Seen' mailbox Sent unseen 

You can also chain doveadm to fetchmail which results in: 

 */3 * * * * fetchmail && doveadm flags add -u <username@localhost> '\Seen' mailbox Sent unseen 


[[Category:Linux]]
[[Kategorie:E-Mail]]