Robtex

Up: 199.36.160.0/21
Can't show all results, try to descend to a more specific CIDR
Down left: 199.36.164.0/23
Down right: 199.36.166.0/23
(Some of the IP numbers are capped at 3 entries)

IP	Type	Hostname
199.36.164.0	PTR	199-36-164-0.schoolmessenger.com
199.36.164.39	A+PTR	ns1.schoolmessenger.com
199.36.164.41	A+PTR	asp.schoolmessenger.com
199.36.164.42	A+PTR	contactme.schoolmessenger.com
199.36.164.43	PTR	calldispatch1.swiftwavenetwork.com
199.36.164.45	A+PTR	ftp.swiftwavenetwork.com
199.36.164.46	A+PTR	smtp1.swiftwavenetwork.com
199.36.164.47	A+PTR	smtp2.swiftwavenetwork.com
199.36.164.48	A+PTR	smtp3.swiftwavenetwork.com
199.36.164.51	PTR	199-36-164-51.schoolmessenger.com
199.36.164.51	A	alrt4.me
199.36.164.51	A	am4.me
199.36.164.52	A	accounts.relianceco.com
199.36.164.53	A	letstai.com
199.36.164.53	A	callback.schoolmessenger.com
199.36.164.56	PTR	199-36-164-56.schoolmessenger.com
199.36.164.56	A	msg.schoolmessenger.com
199.36.164.57	PTR	199-36-164-57.schoolmessenger.com
199.36.164.57	A	pxl.schoolmessenger.com
199.36.164.58	PTR	199-36-164-58.schoolmessenger.com
199.36.164.58	A	go.schoolmessenger.com
199.36.164.58	A	infocenter.schoolmessenger.com
199.36.164.59	PTR	199-36-164-59.schoolmessenger.com
199.36.165.39	A+PTR	ns2.schoolmessenger.com
199.36.165.41	PTR	asp.schoolmessenger.com
199.36.165.42	PTR	contactme.schoolmessenger.com
199.36.165.43	PTR	calldispatch1.swiftwavenetwork.com
199.36.165.45	PTR	ftp.swiftwavenetwork.com
199.36.165.55	PTR	sftp.swiftwavenetwork.com
199.36.166.39	A+PTR	ns3.schoolmessenger.com
199.36.166.41	PTR	asp.schoolmessenger.com
199.36.166.42	PTR	contactme.schoolmessenger.com
199.36.166.43	PTR	calldispatch1.swiftwavenetwork.com
199.36.166.45	PTR	ftp.swiftwavenetwork.com
199.36.167.0	PTR	199-36-167-0.schoolmessenger.com