Lokale Namensauflösung

I have edit the file:

/etc/lighttpd/external.conf
setenv.add-environment = ( "VIRTUAL_HOST" => "invalid.example.com" )

Now the error no longer occurs.
(DataTables warning: table id=messagesTable - Invalid JSON response.)

I have edit the file:
/etc/pihole/pihole-FTL.conf

PIHOLE_PTR=false
PIHOLE_PTR=invalid.example.com

Now:

nslookup invalid.example.com:

Server: invalid.example.com
Address: xx.xx.xx.xx

Name: invalid.example.com
Address: xx.xx.xx.xx

everything looks just fine but

nslookup pi.hole:
Server: invalid.example.com
Address: xx.xx.xx.xx

Name: pi.hole
Addresses: xxxx:xxxx:xxxx:xxxx
xx.xx.xx.xx

The name is still pi.hole an he is still resolving.

Can I change this or stop it?