This issue may manifest in Horde when attempting to change the language of the webmail application but not taking effect.
Or observing similar failure messages when logging in via SSH:
Perl: warning: Setting locale failed.
Perl: warning: Please check that your locale settings:
LANGUAGE = "",
LC_ALL = (unset),
LANG = "es_US.UTF-8"
are supported and installed on your system.
Perl: warning: Falling back to the standard locale ("C").
Missing locales will prevent certain items from being able to translate appropriately or cause other failure messages.
To list the available locales, you may use the following commands to view the currently available locales:
The "glibc-common" package provided by the Operating System includes a standard set of locales that can be listed using this command:
rpm -ql glibc-common|grep -P 'locale\S\w+$'
If a standard locale provided by the Operating System is missing, you may reinstall it by reinstalling the "glibc-common" package, and this will reconfigure the locale-archive.
yum reinstall glibc-common