Am 08.10.18 um 14:06 schrieb Meaulnes Legler@roundcube:

_2nd question:_ how can I get more specific error messages as just a
lapidary « _/!\_ Login failed » ?

have you ever considered to look at your maillog?
roundcube is just a client

yes I did, it just says logged in and logged out.

502# less /var/log/maillog | grep username
Oct  8 14:32:12 blue2 dovecot: imap-login: Login: user=, method=PLAIN, rip=94.103.xx.xx, lip=94.103.xx.xx, mpid=32040, secured, session=
Oct  8 14:32:12 blue2 dovecot: imap(username): Logged out in=29 out=496
503#

so I guess the login was correct but the session obviously doesn't last...

when you see no conenction your config is wrong, when you see
connections you see also what fails

yeah well no clue why the session doesn't stay alive.

Thank you and best regards