Roundcube creates new user with host FQDN instead of localhost

[Tapio Lehtonen]

Debian Stretch, roundcube 1.2.3+dfsg.1-4+deb9u1

Roundcube has created new user_id, with mail_host as FQDN and not 
localhost as previously. last_login with user where mail_host is 
localhost was 21. March, today login is mail_host FQDN.

Can I fix this in the database so address books etc of these two users 
are merged together?

How can I force Roundcube to not do this anymore? I have set
$config['login_lc'] = 2;
to get all lowercase username and domain part, and
$config['default_host'] = 'localhost';
is in both config.inc.php and defaults.inc.php.

--
Tapio Lehtonen
OSK Satatuuli
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