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OS: Linux Ubuntu 20.04
Web server: NGINX
Database: MariaDB

The installer ran on the command line

I have already made the necessary configuration prior to the installation:

• Set DNS records (A & MX records)

• Set FQDN with setting the ’/etc/hosts’ file as
  MyIPAddress mail.MyWebsite.com mail

• Allowed UFW ports 25, 587, 465

• etc., etc..

Then when I try to go to the login pages for iRedMail & RoundCube, I get nothing but a ‘502 bad gateway’ error page.

I thought that iRedMail says to NOT install anything prior to running their installation. I know that their installation is supposed to be a on 'fresh OS’.

Why doesn’t the installation lead me to a working page? What else could I be missing? Am I still supposed to set up my own NGINX Server Blocks and enable sites on this subdomain?

Any support is appreciated.