apt install roundcube

mysql -uroot -p

CREATE DATABASE roundcubemail /*!40101 CHARACTER SET utf8 COLLATE utf8_general_ci */;
create user roundcube@localhost;
set password for roundcube@localhost = password('SuperSecret');
grant all on roundcubemail.* TO roundcube@localhost;
flush privileges;
\q

cd /usr/share/roundcube/SQL/mysql/
mysql -uroundcube -p roundcubemail < mysql.initial.sql

vi /etc/roundcube/apache.conf

Alias /mail /var/lib/roundcube/public_html
...

vi /etc/roundcube/config.inc.php

<?php

$config = [];
$config['db_dsnw'] = 'mysql://roundcube:SuperSecret@localhost/roundcubemail';

$config['default_host'] = [
    'localhost' => 'domain1.local',
    '127.0.0.1' => 'domain2.local'
    ];

$config['default_port'] = 143;
$config['imap_auth_type'] = 'PLAIN';

$config['smtp_server'] = 'localhost';
$config['smtp_port'] = 25;
$config['smtp_user'] = '%u';
$config['smtp_pass'] = '%p';

$config['support_url'] = '';
$config['product_name'] = '';
$config['des_key'] = '$uper-h@rd-w0rd-190623';

$config['username_domain'] = [
    'localhost' => 'domain1.local',
    '127.0.0.1' => 'domain2.local'
    ];

$config['message_sort_col'] = 'date';
$config['message_sort_order'] = 'DESC';
$config['language'] = 'en_US';
$config['skin'] = 'classic';

$config['enable_spellcheck'] = false;

?>

Меняем логотип на свой

/var/lib/roundcube/skins/classic/images/roundcube_logo.png

Меняем favicon на свой

/var/lib/roundcube/skins/classic/images/favicon.ico

Перезагружаем apache

systemctl restart apache2

Заходим в roundcube

http://IP_ADDRESS_SERVER/mail