How to install and integrate Roundcube with Nginx, ISPConfig, and Debian 12.

I have a Debian 11 web server where SquirrelMail was working perfectly, but it stopped working after I upgraded to Debian 12 Bookworm.
I’ve seen tutorials on forums about installing Roundcube, but none of them have worked out.
Given that SquirrelMail doesn't work on Debian 12 Bookworm, why isn't there a standard plan to replace it with Roundcube?
Also, I noticed configuration files in `/usr/local/ispconfig/server/conf/nginx_apps.vhost.master`—what are they for?
I also followed tutorials like https://www.howtoforge.com/perfect-server-debian-12-buster-apache-bind-dovecot-ispconfig-3-2/, but that one is for Apache; I tried adapting it for Nginx without success—I don't know where to place the Roundcube VirtualHost.
I also tried the tutorial https://www.howtoforge.com/using-roundcube-webmail-with-ispconfig-3-on-debian-wheezy-nginx (Using RoundCube Webmail With ISPConfig 3 On Debian Wheezy/Nginx), which involved creating a remote user in ISPConfig, but unfortunately, I couldn't complete the process.
Could you point me to a comprehensive tutorial that covers creating a remote user in ISPConfig and the subsequent steps?
Thanks in advance—I've been struggling with this for days. I managed to install Roundcube using a real domain name, but I can't seem to integrate it with ISPConfig.

 

Thanks, Till, for the reply; I posted this message earlier today.
To keep things simple, let's say I'm going to follow this tutorial:
https://www.howtoforge.com/using-roundcube-webmail-with-ispconfig-3-on-debian-wheezy-nginx
So, I'm starting by creating a remote user named "myroundcube" with the corresponding password.
I have enabled the associated services:
Server functions
Client functions
Mail user functions
Mail alias functions
Mail spamfilter user functions
Mail spamfilter policy functions
Mail fetchmail functions
Mail spamfilter whitelist functions
Mail spamfilter blacklist functions
Mail user filter functions

So, what's next?
It's worth noting that I have already installed Roundcube using the command:
apt-get install roundcube roundcube-plugins roundcube-plugins-extra
Thanks.

 

After creating the remote user, the instructions say this:
Next go to your website in ISPConfig. On the Options tab, you will see the nginx Directives field:
However, what I see doesn't match the image shown.
Could you clarify this for me?
Thanks

 

So, if I understand correctly, I need to add a new site name—like `mondomaineperso5.com`—and then add the following code to the Nginx configuration?


client_max_body_size 100M;
location /roundcube {
root /var/lib/;
index index.php index.html index.htm;
location ~ (.+\.php)$ {
try_files $uri =404;
include /etc/nginx/fastcgi_params;
# To access SquirrelMail, the default user (like www-data on Debian/Ubuntu) must be used
#fastcgi_pass 127.0.0.1:9000;
fastcgi_pass unix:/var/run/php5-fpm.sock;
fastcgi_index index.php;
fastcgi_intercept_errors on;
fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
fastcgi_buffer_size 128k;
fastcgi_buffers 256 4k;
fastcgi_busy_buffers_size 256k;
fastcgi_temp_file_write_size 256k;
}
location ~* /.svn/ {
deny all;
}
location ~* /README|INSTALL|LICENSE|SQL|bin|CHANGELOG$ {
deny all;
}
}
location /webmail {
rewrite ^ /roundcube last;
}

Sorry, it wasn't mentioned that a new site needed to be added for this.
Thanks.

 

So, for every domain that needs to use Roundcube, do I just need to add this snippet of code to the Nginx configuration?
Thanks.

 

Okay Till, I'll move forward with this and keep you posted.
Thanks.