==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version (check /etc/iredmail-release): iRedMail-0.9.9
- Deployed with iRedMail Easy or the downloadable installer? downloadable installer
- Linux/BSD distribution name and version: Ubuntu 18.04
- Store mail accounts in which backend (LDAP/MySQL/PGSQL):  LDAP
- Web server (Apache or Nginx): NGINX
- Manage mail accounts with iRedAdmin-Pro? No
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====

Once I am trying to install passenger on Nginx (Installed with iRedmail package) via:

sudo apt install ruby-full
sudo apt install dirmngr gnupg apt-transport-https ca-certificates
sudo apt-key adv --recv-keys --keyserver hkp://keyserver.ubuntu.com:80 561F9B9CAC40B2F7
sudo apt-get install software-properties-common
sudo add-apt-repository 'deb https://oss-binaries.phusionpassenger.com/apt/passenger bionic main'
sudo apt update
sudo apt install libnginx-mod-http-passenger

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Afterwards, I am adding this config to virtual host:

client_max_body_size 250m;

  passenger_ruby /usr/bin/passenger_free_ruby;
  passenger_enabled on;
  passenger_min_instances 1;

  error_page 502 /502.html;
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Getting an error that using passenger is restricted and not allowed.