mailserver:

Add user: docker exec -it mailserver setup email add user@home.lan password

Required file for roundcube to work without encryption: ./docker-data/roundcube/config/roundcube-custom.php

<?php
$config['imap_conn_options'] = [
  'ssl' => [
    'verify_peer' => false,
    'verify_peer_name' => false,
    'allow_self_signed' => true,
  ],
];
$config['smtp_conn_options'] = [
  'ssl' => [
    'verify_peer' => false,
    'verify_peer_name' => false,
    'allow_self_signed' => true,
  ],
];