Traditionally, there are four Cyrillic codecs: KOI8-R, WINDOWS-1251, CP866 and ISO-8859-5.
Most email clients use the default KOI8-R
After each update to the new version, I add a line
'KOI8-R' => 'KOI8-R ('. $ this-> app-> gettext ('Cyrillic'). ')',
in function:
program / include / rcmail_output_html.php -> open function charset_selector ($ attrib) -> $ charsets = array (
Add this line to the distribution, please.
see https://github.com/roundcube/roundcubemail/pull/6861
Thanks a lot!