@doncamilo: Thanks for your help.
The log file shows me something about DNS difficulties:
2021/02/05 20:43:09 ERROR> Service.pm:971 EBox::Module::Service::restartService - Die DNS-Abfrage ist fehlgeschlagen: NXDOMAIN (Verwendung des Nameservers 127.0.0.1, /etc/resolv.conf war
2021/02/05 20:43:09 ERROR> RestartService.pm:61 EBox::SysInfo::CGI::RestartService::_process - Restart of E-Mail from dashboard failed: Die DNS-Abfrage ist fehlgeschlagen: NXDOMAIN (Verwendung des Nameservers 127.0.0.1, /etc/resolv.conf war
'# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
# and managed by Zentyal.
#
# DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
#
nameserver 127.0.0.1
search lueghi-net.home
'
2021/02/05 20:43:09 DEBUG> Sudo.pm:189 EBox::Sudo::_root - /usr/share/zentyal/psgi/zentyal.psgi (pid: 32062) - /sbin/mii-tool > /var/lib/zentyal/tmp/linkstatus
2021/02/05 20:43:09 DEBUG> Sudo.pm:189 EBox::Sudo::_root - /usr/share/zentyal/psgi/zentyal.psgi (pid: 32062) - systemctl status ebox.openvpn.server.vpn-android | grep 'Loaded: loaded'
2021/02/05 20:43:09 DEBUG> Sudo.pm:189 EBox::Sudo::_root - /usr/share/zentyal/psgi/zentyal.psgi (pid: 32062) - systemctl status 'ebox.openvpn.server.vpn-android' | grep 'Active: active (running)'
2021/02/05 20:43:09 DEBUG> Sudo.pm:189 EBox::Sudo::_root - /usr/share/zentyal/psgi/zentyal.psgi (pid: 32062) - systemctl status ebox.openvpn.server.vpn-zentyal | grep 'Loaded: loaded'
2021/02/05 20:43:09 DEBUG> Sudo.pm:189 EBox::Sudo::_root - /usr/share/zentyal/psgi/zentyal.psgi (pid: 32062) - systemctl status 'ebox.openvpn.server.vpn-zentyal' | grep 'Active: active (running)'
2021/02/05 20:43:09 DEBUG> Sudo.pm:189 EBox::Sudo::_root - /usr/share/zentyal/psgi/zentyal.psgi (pid: 32062) - systemctl status ebox.openvpn.client.stefan | grep 'Loaded: loaded'
2021/02/05 20:43:09 DEBUG> Sudo.pm:189 EBox::Sudo::_root - /usr/share/zentyal/psgi/zentyal.psgi (pid: 32062) - systemctl status 'ebox.openvpn.client.stefan' | grep 'Active: active (running)'
2021/02/05 20:43:09 WARN> zentyal.psgi:43 Plack::Sandbox::_2fusr_2fshare_2fzentyal_2fpsgi_2fzentyal_2epsgi::__ANON__ - Use of uninitialized value $addr in concatenation (.) or string at /usr/share/perl5/EBox/OpenVPN/Client.pm line 565.
2021/02/05 20:43:09 WARN> zentyal.psgi:43 Plack::Sandbox::_2fusr_2fshare_2fzentyal_2fpsgi_2fzentyal_2epsgi::__ANON__ - Use of uninitialized value $port in concatenation (.) or string at /usr/share/perl5/EBox/OpenVPN/Client.pm line 565.
2021/02/05 20:43:09 WARN> zentyal.psgi:43 Plack::Sandbox::_2fusr_2fshare_2fzentyal_2fpsgi_2fzentyal_2epsgi::__ANON__ - Use of uninitialized value $proto in uc at /usr/share/perl5/EBox/OpenVPN/Client.pm line 565.
2021/02/05 20:43:09 DEBUG> Sudo.pm:189 EBox::Sudo::_root - /usr/share/zentyal/psgi/zentyal.psgi (pid: 32062) - systemctl status amavis | grep 'Loaded: loaded'
2021/02/05 20:43:09 DEBUG> Sudo.pm:189 EBox::Sudo::_root - /usr/share/zentyal/psgi/zentyal.psgi (pid: 32062) - systemctl status 'amavis' | grep 'Active: active (running)'
2021/02/05 20:43:10 DEBUG> Sudo.pm:189 EBox::Sudo::_root - /usr/share/zentyal/psgi/zentyal.psgi (pid: 32062) - systemctl status clamav-daemon | grep 'Loaded: loaded'
2021/02/05 20:43:10 DEBUG> Sudo.pm:189 EBox::Sudo::_root - /usr/share/zentyal/psgi/zentyal.psgi (pid: 32062) - systemctl status 'clamav-daemon' | grep 'Active: active (running)'
2021/02/05 20:43:10 DEBUG> Sudo.pm:189 EBox::Sudo::_root - /usr/share/zentyal/psgi/zentyal.psgi (pid: 32062) - systemctl status isc-dhcp-server | grep 'Loaded: loaded'
2021/02/05 20:43:10 DEBUG> Sudo.pm:189 EBox::Sudo::_root - /usr/share/zentyal/psgi/zentyal.psgi (pid: 32062) - systemctl status 'isc-dhcp-server' | grep 'Active: active (running)'
2021/02/05 20:43:10 DEBUG> Sudo.pm:189 EBox::Sudo::_root - /usr/share/zentyal/psgi/zentyal.psgi (pid: 32062) - systemctl status tftpd-hpa | grep 'Loaded: loaded'
2021/02/05 20:43:10 DEBUG> Sudo.pm:189 EBox::Sudo::_root - /usr/share/zentyal/psgi/zentyal.psgi (pid: 32062) - systemctl status 'tftpd-hpa' | grep 'Active: active (running)'
2021/02/05 20:43:10 DEBUG> Sudo.pm:189 EBox::Sudo::_root - /usr/share/zentyal/psgi/zentyal.psgi (pid: 32062) - systemctl status bind9 | grep 'Loaded: loaded'
2021/02/05 20:43:10 DEBUG> Sudo.pm:189 EBox::Sudo::_root - /usr/share/zentyal/psgi/zentyal.psgi (pid: 32062) - systemctl status 'bind9' | grep 'Active: active (running)'
2021/02/05 20:43:11 DEBUG> Sudo.pm:189 EBox::Sudo::_root - /usr/share/zentyal/psgi/zentyal.psgi (pid: 32062) - systemctl status postfix@- | grep 'Loaded: loaded'
2021/02/05 20:43:11 DEBUG> Sudo.pm:189 EBox::Sudo::_root - /usr/share/zentyal/psgi/zentyal.psgi (pid: 32062) - systemctl status 'postfix@-' | grep 'Active: active (running)'
2021/02/05 20:43:11 DEBUG> Sudo.pm:189 EBox::Sudo::_root - /usr/share/zentyal/psgi/zentyal.psgi (pid: 32062) - systemctl status amavis | grep 'Loaded: loaded'
2021/02/05 20:43:11 DEBUG> Sudo.pm:189 EBox::Sudo::_root - /usr/share/zentyal/psgi/zentyal.psgi (pid: 32062) - systemctl status 'amavis' | grep 'Active: active (running)'
2021/02/05 20:43:11 DEBUG> Sudo.pm:189 EBox::Sudo::_root - /usr/share/zentyal/psgi/zentyal.psgi (pid: 32062) - systemctl status zentyal.learnspamd | grep 'Loaded: loaded'
2021/02/05 20:43:11 DEBUG> Sudo.pm:189 EBox::Sudo::_root - /usr/share/zentyal/psgi/zentyal.psgi (pid: 32062) - systemctl status 'zentyal.learnspamd' | grep 'Active: active (running)'
2021/02/05 20:43:11 DEBUG> Sudo.pm:189 EBox::Sudo::_root - /usr/share/zentyal/psgi/zentyal.psgi (pid: 32062) - systemctl status amavis | grep 'Loaded: loaded'
2021/02/05 20:43:11 DEBUG> Sudo.pm:189 EBox::Sudo::_root - /usr/share/zentyal/psgi/zentyal.psgi (pid: 32062) - systemctl status 'amavis' | grep 'Active: active (running)'
2021/02/05 20:43:11 DEBUG> Sudo.pm:189 EBox::Sudo::_root - /usr/share/zentyal/psgi/zentyal.psgi (pid: 32062) - systemctl status ntp | grep 'Loaded: loaded'
2021/02/05 20:43:11 DEBUG> Sudo.pm:189 EBox::Sudo::_root - /usr/share/zentyal/psgi/zentyal.psgi (pid: 32062) - systemctl status 'ntp' | grep 'Active: active (running)'
2021/02/05 20:43:11 DEBUG> Sudo.pm:189 EBox::Sudo::_root - /usr/share/zentyal/psgi/zentyal.psgi (pid: 32062) - systemctl status samba-ad-dc | grep 'Loaded: loaded'
2021/02/05 20:43:11 DEBUG> Sudo.pm:189 EBox::Sudo::_root - /usr/share/zentyal/psgi/zentyal.psgi (pid: 32062) - systemctl status 'samba-ad-dc' | grep 'Active: active (running)'
2021/02/05 20:43:12 DEBUG> Sudo.pm:189 EBox::Sudo::_root - /usr/share/zentyal/psgi/zentyal.psgi (pid: 32062) - systemctl status zentyal.samba-sync | grep 'Loaded: loaded'
2021/02/05 20:43:12 DEBUG> Sudo.pm:189 EBox::Sudo::_root - /usr/share/zentyal/psgi/zentyal.psgi (pid: 32062) - systemctl status 'zentyal.samba-sync' | grep 'Active: active (running)'
2021/02/05 20:43:12 DEBUG> Sudo.pm:189 EBox::Sudo::_root - /usr/share/zentyal/psgi/zentyal.psgi (pid: 32062) - systemctl status sogo | grep 'Loaded: loaded'
2021/02/05 20:43:12 DEBUG> Sudo.pm:189 EBox::Sudo::_root - /usr/share/zentyal/psgi/zentyal.psgi (pid: 32062) - systemctl status 'sogo' | grep 'Active: active (running)'
2021/02/05 20:43:12 INFO> Index.pm:187 EBox::Dashboard::CGI::Index::masonParameters - dashboard1
2021/02/05 20:43:15 DEBUG> Sudo.pm:189 EBox::Sudo::_root - /usr/share/zentyal/psgi/zentyal.psgi (pid: 32062) - dpkg --clear-avail
2021/02/05 20:43:43 DEBUG> Sudo.pm:189 EBox::Sudo::_root - /usr/share/zentyal/psgi/zentyal.psgi (pid: 32062) - /sbin/mii-tool > /var/lib/zentyal/tmp/linkstatus
...
I had to shorten the log because of length restricton.
For /etc/resolv.conf there is a link to
/run/resolvconf/resolv.conf.
But I#m sorry: I don't know what to do or what to check now? My network seems to work well. From my clientc I can ping everything in my domain (by name) and the internet works too ...
The logfile mail.log doesn't exist in my installation
.
The output of
sudo systemctl status postfix@-.service postfix.service
postfix@-.service - Postfix Mail Transport Agent (instance -)
Loaded: loaded (/lib/systemd/system/postfix@.service; indirect; vendor preset: enabled)
Active: inactive (dead)
Docs: man:postfix(1)
● postfix.service - Postfix Mail Transport Agent
Loaded: loaded (/lib/systemd/system/postfix.service; disabled; vendor preset: enabled)
Active: inactive (dead)