Robtex

Up: 69.56.16.0/21
Can't show all results, try to descend to a more specific CIDR
Down left: 69.56.16.0/23
Down right: 69.56.18.0/23
(Some of the IP numbers are capped at 3 entries)

IP	Type	Hostname
69.56.16.2	A	mta.skylist.com
69.56.18.25	A+PTR	mail1.email.carnegiecomm.com
69.56.18.26	A	mail2.email.carnegiecomm.com
69.56.18.27	PTR	mail3.members.alloyeducation.com
69.56.18.27	A	mail3.email.carnegiecomm.com
69.56.18.28	A	mail4.email.carnegiecomm.com
69.56.18.29	A	mail5.email.carnegiecomm.com
69.56.18.30	A	mail6.email.carnegiecomm.com
69.56.18.31	PTR	mail7.members.alloyeducation.com
69.56.18.31	A	mail7.email.carnegiecomm.com
69.56.18.32	A	members.alloystudentoffers.com
69.56.18.33	A	mail1.members.alloystudentoffers.com
69.56.18.34	A	mail2.members.alloystudentoffers.com
69.56.18.35	A	mail3.members.alloystudentoffers.com
69.56.18.39	A	mail7.members.alloystudentoffers.com
69.56.18.40	A+PTR	click1.members.privatecolleges.com
69.56.18.40	A	webmail.members.privatecolleges.com
69.56.18.40	A	mail.members.privatecolleges.com
69.56.18.46	PTR	mail6.members.privatecolleges.com
69.56.18.48	PTR	click1.members.collegexpress.com
69.56.18.48	A	members.collegexpress.com
69.56.18.49	PTR	mail1.members.collegexpress.com
69.56.18.50	PTR	mail2.members.collegexpress.com
69.56.18.51	PTR	mail3.members.collegexpress.com
69.56.18.52	A+PTR	mail4.members.collegexpress.com
69.56.18.53	PTR	mail5.members.collegexpress.com
69.56.18.54	PTR	mail6.members.collegexpress.com
69.56.18.55	A+PTR	mail7.members.collegexpress.com
69.56.19.16	A	webmail.members.vault.com
69.56.19.16	A	click1.members.vault.com
69.56.19.16	A	members.vault.com
69.56.19.22	A	mail6.members.vault.com
69.56.19.24	PTR	click1.info.vault.com
69.56.19.24	A	info.vault.com
69.56.19.25	A	mail1.info.vault.com
69.56.19.26	A	mail2.info.vault.com
69.56.19.27	PTR	mail3.info.vault.com
69.56.19.31	A	mail7.info.vault.com
69.56.19.32	A	careerinsider-news.vault.com
69.56.19.34	A	mail2.careerinsider-news.vault.com
69.56.19.40	PTR	click1.email.infobaselearning.com
69.56.19.40	A	email.infobaselearning.com
69.56.19.43	A	mail3.email.infobaselearning.com
69.56.19.44	PTR	mail4.email.infobaselearning.com