mail config settings in multiserver set-up - roundcube - connection to storage server failed

hi all
need your assistance to give me a direction in debugging - i have followed the perfect multiserver tutorial for debian 10.
the issue to resolve is that when going to '192.168.1.39/webmail' or 'webmail.example.com/webmail' i get the roundcube error message 'connection to storage server failed'

current settings (Note: currently using external DNS provider (i.e. haven't yet set-up and started using the DNS service in ISPConfig):

Code:

mx1.example.com with individual A record pointing to 192.168.1.35
mx2.example.com with individual A record pointing to 192.168.1.36
webmail.example.com with individual A record pointing to 192.168.1.39

roundcube config

Code:

$config['default_host'] = 'ssl://mx2.example.com';
$config['smtp_server'] = 'tls://mx1.example.com';
$config['smtp_port'] = 587;

what configuration needs to get set to enable roundcube usage? what options do i have to de-bug?

thanks!

OS

Code:

root@web01:~# lsb_release -a
No LSB modules are available.
Distributor ID:    Debian
Description:    Debian GNU/Linux 10 (buster)
Release:    10
Codename:    buster

php version

Code:

root@web01:~# php -v
PHP 7.3.31-1+0~20210923.88+debian10~1.gbpac4058 (cli) (built: Sep 23 2021 22:03:28) ( NTS )
Copyright (c) 1997-2018 The PHP Group
Zend Engine v3.3.31, Copyright (c) 1998-2018 Zend Technologies
    with Zend OPcache v7.3.31-1+0~20210923.88+debian10~1.gbpac4058, Copyright (c) 1999-2018, by Zend Technologies

 

First thing to check is you really have followed the instructions in the tutorial accurately.
Then do this:
https://www.howtoforge.com/community/threads/please-read-before-posting.58408/
You wrote the error message is 'connection to storage server failed'. I would check the /etc/hosts file on every host in your setup is correct and has all the hosts listed. Other than that, try to see if log files give more info or use Internet Search Engines with that error message.