Currently login_lc has value false. But the docs athttps://github.com/roundcube/roundcubemail/wiki/Configuration
state the possible values are 0, 1 and 2.
main.inc.php:$rcmail_config['login_lc'] = false;
Is that false a remnant from older versions? Seems I need to put 2 there, the duplicate names are
jarkko@somedomain and Jarkko@somedomain, so the user name part needs to be lowercased.
The default_host is localhost. Seems it was previously tls://<fqdn>, but I think it should be localhost when the
mail server and roundcube are on the same host.
It seems some gremlin has created extra users to roundcube database. Like, for user x that has logged in there are both
mail_host localhost and the fqdm, and for both those x@ and X@ usernames.
I think I now understand what is going on, and can go and fix the mess. Thank you for your help.