==== Required information ====
- iRedMail version (check /etc/iredmail-release): 1.2.0
- Linux/BSD distribution name and version: debian
- Store mail accounts in which backend (LDAP/MySQL/PGSQL):
- Web server (Apache or Nginx): nginx
- Manage mail accounts with iRedAdmin-Pro?
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====

When i configure the  nginx  .conf  (vhost) whit the  roundcube.tmpl in the domain.com.conf.

server {
    listen 443;
    server_name domain.com  www.domainl.com ;
   

    ssl on;
    ssl_certificate /etc/ssl/certs/iRedMail.crt;
    ssl_certificate_key /etc/ssl/private/iRedMail.key;
    ssl_protocols TLSv1 TLSv1.1 TLSv1.2;

    # Fix 'The Logjam Attack'.
    ssl_ciphers ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-DSS-AES128-GCM-SHA256:kEDH+AESGCM:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA:ECDHE-ECDSA-AES128-SHA:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA:ECDHE-ECDSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES128-SHA:DHE-DSS-AES128-SHA256:DHE-RSA-AES256-SHA256:DHE-DSS-AES256-SHA:DHE-RSA-AES256-SHA:ECDHE-RSA-DES-CBC3-SHA:ECDHE-ECDSA-DES-CBC3-SHA:AES128-GCM-SHA256:AES256-GCM-SHA384:AES128-SHA256:AES256-SHA256:AES128-SHA:AES256-SHA:AES:CAMELLIA:DES-CBC3-SHA:!aNULL:!eNULL:!EXPORT:!DES:!RC4:!MD5:!PSK:!aECDH:!EDH-DSS-DES-CBC3-SHA:!EDH-RSA-DES-CBC3-SHA:!KRB5-DES-CBC3-SHA;
    ssl_prefer_server_ciphers on;
    ssl_dhparam /etc/ssl/dh2048_param.pem;

    index index.php index.html;

    location / {
        root /var/www/psa/html;
    }

    # HTTP Strict Transport Security (HSTS)
    #include /etc/nginx/templates/hsts.tmpl;

    # Web applications.
    include /etc/nginx/templates/roundcube.tmpl;
    include /etc/nginx/templates/iredadmin.tmpl;
    include /etc/nginx/templates/sogo.tmpl;

    # PHP applications. WARNING: php-catchall.tmpl should be loaded after
    # other php web applications.
    include /etc/nginx/templates/php-catchall.tmpl;

    include /etc/nginx/templates/misc.tmpl;
}

I have this issue on web page:

INET_E_REDIRECT_FAILED  ( Windows Edge)
iredmail 53/5000 The page is not being redirected correctly  ( Firefox)

Logs:
"GET /mail HTTP/1.1" 302 154 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:56.0) Gecko/20100101 Firefox/56.0"

--------------------------
I TRY :
--------------------------

1) Delete all records in SQL table `iredadmin.session`.  (NO HAVE RESULT)
2) Make sudo ln -s /opt/www/roundcubemail in /www/html/  ( NO HAVE RESULT)

-------------------------
SOLUTION
--------------------------

I use cloudflare  ,   i go to   Crypto  and change SSL CERTIFICATE  Flexible ->  FULL.

And this working!
Thanx