*.pool.ntp.casjay.nl has no SRV records.
Question and response
Question
dig casjay.pool.ntp.org. SRV
Answer
The response has no answer records.
Authority
pool.ntp.org. 1300 SOA c.ntpns.org. hostmaster.pool.ntp.org. 1772866673 5400 5400 1209600 3600
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0