==== Required information ====
- iRedMail version (check /etc/iredmail-release): 0.9.6
- Linux/BSD distribution name and version: Debian 8
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): mysql
- Web server (Apache or Nginx):nginx
- Manage mail accounts with iRedAdmin-Pro? no
- Related log if you're reporting an issue:
====
In folder /opt/www/roundcubemail
files has mostly owner 501 and group 80

-rw-r--r--  1      501       80   3403 Nov 27 16:07 UPGRADING
-rw-r--r--  1      501 staff      9954 Nov 27 16:07 INSTALL
so on
files and folders in plugins folder  owner and group is 501:80

and some www-data, and root

in /etc/passwd and /etc/group there is no user/group 501, 80 or staff.

roundcube upgraded from: http://www.iredmail.org/yum/misc/roundc … ete.tar.gz

Used this instruction to upgrade:
cd <the-unpacked-roundcube-directory>
bin/installto.sh <your-existing-roundcube-directory>

any advice on that?

Thanks!