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

Results formx.securemx.jp

Resolver

Location

A

Name	TTL	Value
mx.securemx.jp	600	210.130.202.92IIJ Internet / Internet Initiative Japan Inc.
mx.securemx.jp	600	210.130.202.93IIJ Internet / Internet Initiative Japan Inc.
mx.securemx.jp	600	210.130.202.96IIJ Internet / Internet Initiative Japan Inc.
mx.securemx.jp	600	210.130.202.99IIJ Internet / Internet Initiative Japan Inc.