Question and response
Question
dig _netblocks.blackboard.com. TXT
Answer
_netblocks.blackboard.com. 300 TXT "v=spf1 ip4:23.96.16.19 ip4:40.76.211.14 ip4:192.207.19.168 -all"
Authority
blackboard.com. 172800 NS ns-1321.awsdns-37.org.
blackboard.com. 172800 NS ns-1824.awsdns-36.co.uk.
blackboard.com. 172800 NS ns-337.awsdns-42.com.
blackboard.com. 172800 NS ns-719.awsdns-25.net.
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0