It can be anything! An apex, subdomain, or even a URL.

Results formx.cam.ac.uk

Resolver

Location

A

Name	TTL	Value
mx.cam.ac.uk	3600	131.111.8.146University of Cambridge / Jisc Services Limited
mx.cam.ac.uk	3600	131.111.8.147University of Cambridge / Jisc Services Limited
mx.cam.ac.uk	3600	131.111.8.148University of Cambridge / Jisc Services Limited
mx.cam.ac.uk	3600	131.111.8.149University of Cambridge / Jisc Services Limited

Name	TTL	Value
mx.cam.ac.uk	3600	v=spf1 ip6:2a05:b400::/32 ip6:2a00:1098:5::/48 ip6:2001:630:210::/44 ip4:131.111.0.0/16 ip4:128.232.0.0/16 ip4:129.169.0.0/16 ip4:192.18.195.0/24 ip4:192.84.5.0/24 ip4:192.153.213.0/24 ip4:193.60.80.0/20 ip4:193.63.252.0/23