Issue description: I have two servers with ISPConfig 3.1.13 using a multi-server setup and one control interface only. I have set the primary server as Primary DNS, and under "Client > Limits (tab) > DNS Server I have configured as follow: When I update the DNS the second server gets notified and does nothing. Under /etc/named.conf.local the zone is set as master on the second server (as well as in the first) but this file is largely outdated. I haven't edited files manually. Also, new domains I add are not transferred to the second server. Environment: Server OS: CentOS Server OS version: CentOS 7 ISPConfig version: 3.1.13 On the master server: Code: Sep 12 10:30:03 de-pri named: zone lostroom.pt/IN: loaded serial 2018091212 (DNSSEC signed) Sep 12 10:30:03 de-pri named: zone lostroom.pt/IN: sending notifies (serial 2018091212) On the secondary server: Code: (old) Sep 12 09:36:02 de-seg named: client 184.108.40.206#47877: received notify for zone 'lostroom.pt' ... (old) Sep 12 10:02:03 de-seg named: client 220.127.116.11#12705: received notify for zone 'lostroom.pt' ... Sep 12 10:30:03 de-seg named: client 18.104.22.168#5571: received notify for zone 'lostroom.pt' Querying master: Code: horus:~ mendesrm$ dig @de-pri.gdcltd.pt lostroom.pt SOA +short de-pri.gdcltd.pt. admin.lostroom.pt. 2018091212 7200 540 604800 3600 Querying slave: Code: horus:~ mendesrm$ dig @de-seg.gdcltd.pt lostroom.pt SOA +short de-pri.gdcltd.pt. admin.gdcltd.pt. 2018091001 7200 540 604800 3600 Thank you.