Robtex

Up: 74.91.80.0/21
Can't show all results, try to descend to a more specific CIDR
Down left: 74.91.80.0/23
Down right: 74.91.82.0/23
(Some of the IP numbers are capped at 3 entries)

IP	Type	Hostname
74.91.80.3	PTR	mailer3.gate80.rs.smtp.com
74.91.80.6	A	mailer6.gate80.rs.smtp.com
74.91.80.7	A+PTR	mailer7.gate80.rs.smtp.com
74.91.80.8	PTR	mailer8.gate80.rs.smtp.com
74.91.80.9	A	mailer9.gate80.rs.smtp.com
74.91.80.14	PTR	mailer14.gate80.rs.smtp.com
74.91.80.20	A+PTR	mailer20.gate80.rs.smtp.com
74.91.80.22	A+PTR	mailer22.gate80.rs.smtp.com
74.91.80.32	PTR	mailer32.gate80.rs.smtp.com
74.91.80.34	A	mailer34.gate80.rs.smtp.com
74.91.80.36	PTR	mailer36.gate80.rs.smtp.com
74.91.80.41	A	mailer41.gate80.rs.smtp.com
74.91.80.42	PTR	mailer42.gate80.rs.smtp.com
74.91.80.43	PTR	mailer43.gate80.rs.smtp.com
74.91.80.44	A	mailer44.gate80.rs.smtp.com
74.91.80.47	PTR	mailer47.gate80.rs.smtp.com
74.91.80.48	PTR	mailer48.gate80.rs.smtp.com
74.91.80.49	A	mailer49.gate80.rs.smtp.com
74.91.80.50	A	mailer50.gate80.rs.smtp.com
74.91.80.53	PTR	mailer53.gate80.rs.smtp.com
74.91.80.55	A	mailer55.gate80.rs.smtp.com
74.91.80.68	A	mailer68.gate80.rs.smtp.com
74.91.80.90	PTR	90-80.he.smtp.com
74.91.80.123	PTR	123-80.he.smtp.com
74.91.80.186	A	mailer186.gate80.rs.smtp.com
74.91.80.201	A+PTR	mailer201.gate80.rs.smtp.com
74.91.80.209	A	mailer209.gate80.rs.smtp.com
74.91.80.235	A	mailer235.gate80.rs.smtp.com
74.91.80.238	A	mailer238.gate80.rs.smtp.com
74.91.81.7	A	he-mgmt02.smtp.com
74.91.81.100	A+PTR	mailer100.gate81.rs.smtp.com
74.91.81.105	A	mailer105.gate81.rs.smtp.com
74.91.81.106	PTR	mailer106.gate81.rs.smtp.com
74.91.81.110	A	mailer110.gate81.rs.smtp.com
74.91.81.117	PTR	mailer117.gate81.rs.smtp.com
74.91.81.120	A	mailer120.gate81.rs.smtp.com
74.91.81.122	PTR	mailer122.gate81.rs.smtp.com
74.91.81.142	A+PTR	mailer142.gate81.rs.smtp.com
74.91.81.143	A+PTR	mailer143.gate81.rs.smtp.com
74.91.81.201	A	mailer201.gate81.rs.smtp.com
74.91.81.217	A+PTR	mailer217.gate81.rs.smtp.com
74.91.81.218	PTR	218-81.he.smtp.com
74.91.81.240	PTR	240-81.he.smtp.com
74.91.82.1	A+PTR	mailer1.gate82.rs.smtp.com
74.91.82.4	A+PTR	mailer4.gate82.rs.smtp.com
74.91.82.10	PTR	mailer10.gate82.rs.smtp.com
74.91.83.10	A+PTR	mailer10.gate83.rs.smtp.com
74.91.83.20	A+PTR	mailer20.gate83.rs.smtp.com
74.91.83.22	A+PTR	mailer22.gate83.rs.smtp.com
74.91.83.32	PTR	mailer32.gate83.rs.smtp.com
74.91.83.46	PTR	mailer46.gate83.rs.smtp.com
74.91.83.60	A	messagesmtp.com
74.91.83.92	PTR	mailer92.gate83.rs.smtp.com
74.91.83.103	PTR	mailer103.gate83.rs.smtp.com
74.91.83.111	A	mailer111.gate83.rs.smtp.com
74.91.83.112	A	mailer112.gate83.rs.smtp.com
74.91.83.113	A	mailer113.gate83.rs.smtp.com
74.91.83.124	A	mailer124.gate83.rs.smtp.com
74.91.83.128	PTR	128.pro.he.smtp.com
74.91.83.132	A	mailer132.gate83.rs.smtp.com
74.91.83.140	A	rs-ord-mtsp-mta04-1.smtp.com
74.91.83.158	A	rs-ord-mta02-out1.smtp.com
74.91.83.161	A	rs-ord-mta04-2.smtp.com
74.91.83.165	A	rs-ord-mta03-2.smtp.com
74.91.83.171	PTR	mailer171.gate83.rs.smtp.com
74.91.83.171	A	smtpin1.smtp.com
74.91.83.176	PTR	176.pro.he.smtp.com
74.91.83.181	PTR	mailer181.gate83.rs.smtp.com
74.91.83.181	A	in1touch.smtp.com
74.91.83.181	A	agqa.smtp.com
74.91.83.182	PTR	mailer182.gate83.rs.smtp.com
74.91.83.182	A	in1touch.smtp.com
74.91.83.182	A	agqa.smtp.com
74.91.83.191	A+PTR	mailer191.gate83.rs.smtp.com
74.91.83.204	PTR	mailer204.gate83.rs.smtp.com
74.91.83.204	A	smtpsend.com
74.91.83.204	A	smtpsendmail.com
74.91.83.207	PTR	mailer207.gate83.rs.smtp.com
74.91.83.207	A	go.agm1.us
74.91.83.207	A	go.transsender.net
74.91.83.208	PTR	mailer208.gate83.rs.smtp.com
74.91.83.208	A	go.agm1.us
74.91.83.208	A	rs-beacon-2.smtp.com