I have roundcube 1.6.7 installed, with the default skin “elastic”.
I have several options changed in “config.inc.php” — the configuration file for roundcube. The are listed as follows.
# how roundcube talks to mailserver, here for smtp/imap we use SSL only
$config['imap_host'] = 'ssl://mail.sample.com:993';
$config['smtp_host'] = 'ssl://mail.sample.com:465';
# managesieve plugin is enabled for filters
$config['plugins'] = ['managesieve'];
# don't let roundcube auto-detect user language, use en_US by default
$config['language'] = 'en_US';
# webmail session timeout (one day)
$config['session_lifetime'] = 1440;
# logo and favicon
$config['skin_logo'] = 'https://sample.com/logo.png';
# disable users to edit their identities
$config['identities_level'] = 3;
With these customized options I have got an acceptable webmail system, which works fine on either PC or mobile.