Robtex

Up: 221.133.4.0/22
Can't show all results, try to descend to a more specific CIDR
Down left: 221.133.6.0/24
Down right: 221.133.7.0/24
(Some of the IP numbers are capped at 3 entries)

IP	Type	Hostname
221.133.7.2	PTR	mail.emailmarketing.saigonnet.vn
221.133.7.3	PTR	mail.emailmarketing.saigonnet.vn
221.133.7.4	PTR	mail.emailmarketing.saigonnet.vn
221.133.7.5	PTR	mail.emailmarketing.saigonnet.vn
221.133.7.6	PTR	mail.emailmarketing.saigonnet.vn
221.133.7.7	PTR	mail.emailmarketing.saigonnet.vn
221.133.7.8	PTR	mail.emailmarketing.saigonnet.vn
221.133.7.9	PTR	mail.emailmarketing.saigonnet.vn
221.133.7.10	PTR	mail.emailmarketing.saigonnet.vn
221.133.7.11	PTR	mail.emailmarketing.saigonnet.vn
221.133.7.12	PTR	mail.emailmarketing.saigonnet.vn
221.133.7.13	PTR	mail.emailmarketing.saigonnet.vn
221.133.7.14	PTR	mail.emailmarketing.saigonnet.vn
221.133.7.15	PTR	mail.emailmarketing.saigonnet.vn
221.133.7.16	PTR	mail.emailmarketing.saigonnet.vn
221.133.7.17	PTR	mail.emailmarketing.saigonnet.vn
221.133.7.18	PTR	mail.emailmarketing.saigonnet.vn
221.133.7.19	PTR	mail.emailmarketing.saigonnet.vn
221.133.7.20	PTR	mail.emailmarketing.saigonnet.vn
221.133.7.21	PTR	mail.emailmarketing.saigonnet.vn
221.133.7.22	PTR	mail.emailmarketing.saigonnet.vn
221.133.7.23	PTR	mail.emailmarketing.saigonnet.vn
221.133.7.24	PTR	mail.emailmarketing.saigonnet.vn
221.133.7.25	PTR	mail.emailmarketing.saigonnet.vn
221.133.7.26	PTR	mail.emailmarketing.saigonnet.vn
221.133.7.27	PTR	mail.emailmarketing.saigonnet.vn
221.133.7.28	PTR	mail.emailmarketing.saigonnet.vn
221.133.7.29	PTR	mail.emailmarketing.saigonnet.vn
221.133.7.30	A+PTR	mail.emailmarketing.saigonnet.vn
221.133.7.30	A	emailmarketing.saigonnet.vn
221.133.7.58	A	vuivuibay.com
221.133.7.58	A	ns4.tenten.vn.baybay.vn
221.133.7.58	A	baybay.vn
221.133.7.86	A	findinbag.com
221.133.7.92	A	saigonpost.vn
221.133.7.92	A	sgp.vn
221.133.7.104	A	mail.support.ipt.vn
221.133.7.104	A	support.ipt.vn
221.133.7.106	A	dangkytenmien.vn
221.133.7.106	A	www.dangkytenmien.vn
221.133.7.120	A	stc.spt.vn
221.133.7.120	A	btvtech.vn
221.133.7.120	A	mobifone-retail.com
221.133.7.122	A	spt.vn
221.133.7.124	A	web47.ipt.vn
221.133.7.161	A	ads7.s-wifi.vn
221.133.7.161	A	auth3.s-wifi.vn
221.133.7.161	A	delivery.s-wifi.vn
221.133.7.162	A	media.s-wifi.vn
221.133.7.165	A	s-wifi.net
221.133.7.171	A+PTR	mail.s-wifi.vn
221.133.7.171	A	mail.s-buy.vn
221.133.7.176	A	s-buy.vn
221.133.7.234	A	data.s-wifi.vn