Thank you for your helpful message!
Okay, here's the story of what happened:
The primary DNS server is apparently down:
$ host -a thedndsanctuary.eu ns01.weservit.nl
Trying "thedndsanctuary.eu"
;; connection timed out; no servers could be reached
The secondary DNS server is fine:
$ host -a thedndsanctuary.eu ns02.weservit.eu
Trying "thedndsanctuary.eu"
Using domain server:
Name: ns02.weservit.eu
Address: 83.96.159.200#53
Aliases:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 11323
;; flags: qr aa rd; QUERY: 1, ANSWER: 6, AUTHORITY: 0, ADDITIONAL: 3
;; QUESTION SECTION:
;thedndsanctuary.eu. IN ANY
;; ANSWER SECTION:
thedndsanctuary.eu. 100 IN SOA ns01.weservit.nl. hostmaster.thedndsanctuary.eu. 2014020400 100 3600 1209600 86400
thedndsanctuary.eu. 100 IN NS ns01.weservit.nl.
thedndsanctuary.eu. 100 IN NS ns02.weservit.eu.
thedndsanctuary.eu. 100 IN A 176.56.224.34
thedndsanctuary.eu. 100 IN MX 10 mail.thedndsanctuary.eu.
thedndsanctuary.eu. 100 IN TXT "v=spf1 a mx ip4:176.56.224.34 ~all"
;; ADDITIONAL SECTION:
ns01.weservit.nl. 14400 IN A 94.228.215.20
ns02.weservit.eu. 14400 IN A 83.96.159.200
mail.thedndsanctuary.eu. 100 IN A 176.56.224.34
Received 273 bytes from 83.96.159.200#53 in 24 ms
But! Unfortunately there a typo snuck into the DNS record back when we set it up:
$ host -t ns thedndsanctuary.eu
thedndsanctuary.eu name server ns01.weservit.eu.
thedndsanctuary.eu name server ns01.weservit.nl.
It's fixed now:
$ host -t ns thedndsanctuary.eu
thedndsanctuary.eu name server ns01.weservit.nl.
thedndsanctuary.eu name server ns02.weservit.eu.
I apologize for any inconvenience.