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

Results forwebmail.mikematic.com

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2020-01-14T18:29:42.342	2020-01-14T00:00:00	2020-04-13T23:59:59	mikematic.com	webmail.mikematic.com	C=US, ST=TX, L=Houston, O="cPanel, Inc.", CN="cPanel, Inc. Certification Authority"
2020-01-14T18:29:27.421	2020-01-14T00:00:00	2020-04-13T23:59:59	mikematic.com	webmail.mikematic.com	C=US, ST=TX, L=Houston, O="cPanel, Inc.", CN="cPanel, Inc. Certification Authority"
2019-03-31T14:06:13.987	2019-03-31T00:00:00	2019-06-29T23:59:59	m1k3ma71c.ethiohub.com	webmail.mikematic.com	C=US, ST=TX, L=Houston, O="cPanel, Inc.", CN="cPanel, Inc. Certification Authority"
2019-03-31T14:05:58.937	2019-03-31T00:00:00	2019-06-29T23:59:59	m1k3ma71c.ethiohub.com	webmail.mikematic.com	C=US, ST=TX, L=Houston, O="cPanel, Inc.", CN="cPanel, Inc. Certification Authority"