I could not configure app in phone and PC (tried myMail, Aqua Mail, and Thunderbird on PC). When I tried add account I’ve error (screenshot from aqua mail attached. In kei.pl I have registered my domain).
My site, Direct Admin and roundcube works well under SSL
My domain is: digitaldruk.pl
My web server is: apache 2.4.43
The operating system my web server runs on is: Centos 7.7
I can login to a root shell on my machine: yes
I’m using a control panel to manage my site: Direct Admin 1.6
77.91.61.189 Włocławek/Kujawsko-Pomorskie/Poland (PL) - Sat Film Sp. z o.o Hostname: user61-189.otwarta.pl
yes
1
0
AAAA
yes
www.digitaldruk.pl
A
77.91.61.189 Włocławek/Kujawsko-Pomorskie/Poland (PL) - Sat Film Sp. z o.o Hostname: user61-189.otwarta.pl
yes
1
0
AAAA
yes
is used. But may be there doesn't run a mail server.
If the mail server runs on that ip - 94.152.2.64 -, you must use kei.pl as domain name to connect, if your provider doesn't support certificates with customer domains.