Robtex

Up: 103.13.68.0/23
Can't show all results, try to descend to a more specific CIDR
Down left: 103.13.69.0/25
Down right: 103.13.69.128/25
(Some of the IP numbers are capped at 3 entries)

IP	Type	Hostname
103.13.69.12	A+PTR	login-au.mimecast.com
103.13.69.13	A+PTR	bin-au-api.mimecast.com
103.13.69.14	A+PTR	mso4-au.mimecast.com
103.13.69.14	A+PTR	mso4-au-a.mimecast.com
103.13.69.15	A	security-au.mimecast.com
103.13.69.16	A+PTR	service-au.mimecast.com
103.13.69.17	A+PTR	webmail-au.mimecast.com
103.13.69.17	A+PTR	twcmail-au.mimecast.com
103.13.69.19	A+PTR	xdk-au.mimecast.com
103.13.69.19	A+PTR	protect-au.mimecast.com
103.13.69.19	A+PTR	au-api.mimecast.com
103.13.69.22	A+PTR	au-smtp-2.mimecast.com
103.13.69.22	A+PTR	au-smtp-1.mimecast.com
103.13.69.22	A+PTR	au-pop.mimecast.com
103.13.69.24	PTR	au-smtp-2.mimecast.com
103.13.69.26	A+PTR	au-smtp-inbound-1.mimecast.com
103.13.69.26	A+PTR	au-smtp-inbound-2.mimecast.com
103.13.69.26	A	mx2.cqu.edu.au
103.13.69.28	A+PTR	au-smtp-outbound-1.mimecast.com
103.13.69.28	A+PTR	au-smtp-outbound-2.mimecast.com
103.13.69.30	A+PTR	au-smtp-journal-2.mimecast.com
103.13.69.30	A+PTR	au-smtp-journal-1.mimecast.com
103.13.69.32	A+PTR	au-smtp-o365-outbound-1.mimecast.com
103.13.69.32	A+PTR	au-smtp-o365-outbound-2.mimecast.com
103.13.69.36	A+PTR	lfs-au.mimecast.com
103.13.69.37	PTR	static-au.mimecast.com
103.13.69.37	A+PTR	console-au-1.mimecast.com
103.13.69.37	A+PTR	console-au.mimecast.com
103.13.69.38	A+PTR	static-au.mimecast.com
103.13.69.38	PTR	console-au-3.mimecast.com
103.13.69.38	PTR	console-au.mimecast.com
103.13.69.39	A+PTR	au-api-1.mimecast.com
103.13.69.89	A+PTR	au-ftp.mimecast.com
103.13.69.89	A	au-ingftp.mimecast.com
103.13.69.91	A+PTR	au-smtp-outbound1.mimecast.com
103.13.69.92	A+PTR	au-smtp-outbound2.mimecast.com
103.13.69.93	A+PTR	au-smtp-outbound3.mimecast.com
103.13.69.94	A+PTR	au-smtp-outbound4.mimecast.com
103.13.69.95	A+PTR	au-smtp-outbound5.mimecast.com
103.13.69.96	A+PTR	au-smtp-outbound6.mimecast.com
103.13.69.97	A+PTR	au-smtp-outbound7.mimecast.com
103.13.69.98	A+PTR	au-smtp-outbound1-backup.mimecast.com
103.13.69.101	A+PTR	au-smtp-delivery-1.mimecast.com
103.13.69.102	A+PTR	au-smtp-delivery-2.mimecast.com
103.13.69.103	A+PTR	au-smtp-delivery-3.mimecast.com
103.13.69.104	A+PTR	au-smtp-delivery-4.mimecast.com
103.13.69.105	A+PTR	au-smtp-delivery-5.mimecast.com
103.13.69.106	A+PTR	au-smtp-delivery-6.mimecast.com
103.13.69.107	A+PTR	au-smtp-delivery-7.mimecast.com
103.13.69.108	A+PTR	au-smtp-delivery-1-backup.mimecast.com
103.13.69.111	PTR	au-smtp-delivery-11.mimecast.com
103.13.69.112	PTR	au-smtp-delivery-12.mimecast.com
103.13.69.113	PTR	au-smtp-delivery-13.mimecast.com
103.13.69.114	PTR	au-smtp-delivery-14.mimecast.com
103.13.69.115	PTR	au-smtp-delivery-15.mimecast.com
103.13.69.116	PTR	au-smtp-delivery-16.mimecast.com
103.13.69.117	PTR	au-smtp-delivery-17.mimecast.com
103.13.69.118	PTR	au-smtp-delivery-18.mimecast.com
103.13.69.119	PTR	au-smtp-delivery-19.mimecast.com
103.13.69.120	PTR	au-smtp-delivery-20.mimecast.com
103.13.69.121	PTR	au-smtp-delivery-21.mimecast.com
103.13.69.121	A	au-smtp-1.mimecast.com
103.13.69.122	A+PTR	au-smtp-inbound-2.mimecast.com
103.13.69.122	A+PTR	au-smtp-inbound-1.mimecast.com
103.13.69.123	PTR	au-smtp-delivery-23.mimecast.com
103.13.69.123	A	au-smtp-outbound-2.mimecast.com
103.13.69.124	PTR	au-smtp-delivery-24.mimecast.com
103.13.69.125	PTR	au-smtp-o365-outbound-1.mimecast.com
103.13.69.125	A+PTR	au-smtp-o365-outbound-2.mimecast.com
103.13.69.126	PTR	au-smtp-delivery-26.mimecast.com
103.13.69.127	PTR	au-smtp-delivery-27.mimecast.com
103.13.69.128	PTR	au-smtp-delivery-28.mimecast.com
103.13.69.129	PTR	au-smtp-delivery-29.mimecast.com
103.13.69.130	PTR	au-smtp-delivery-30.mimecast.com
103.13.69.131	PTR	au-smtp-delivery-31.mimecast.com
103.13.69.132	PTR	au-smtp-delivery-32.mimecast.com
103.13.69.133	PTR	au-smtp-delivery-33.mimecast.com
103.13.69.134	PTR	au-smtp-delivery-34.mimecast.com
103.13.69.135	PTR	au-smtp-delivery-35.mimecast.com
103.13.69.136	PTR	au-smtp-delivery-36.mimecast.com
103.13.69.137	PTR	au-smtp-delivery-37.mimecast.com
103.13.69.138	PTR	au-smtp-delivery-38.mimecast.com
103.13.69.139	PTR	au-smtp-delivery-39.mimecast.com
103.13.69.140	PTR	au-smtp-delivery-40.mimecast.com
103.13.69.222	A+PTR	au-smtp-inbound-2.mimecast.com
103.13.69.222	A+PTR	au-smtp-inbound-1.mimecast.com
103.13.69.225	A	au-smtp-o365-outbound-2.mimecast.com
103.13.69.250	A+PTR	au-res-1.mimecast.com