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

Results forwebmail.cloudcabinarts.com

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2018-07-18T14:18:00.06	2018-07-18T00:00:00	2018-10-16T23:59:59	cloudcabinarts.com	webmail.cloudcabinarts.com	C=US, ST=TX, L=Houston, O="cPanel, Inc.", CN="cPanel, Inc. Certification Authority"
2018-07-18T14:17:43.832	2018-07-18T00:00:00	2018-10-16T23:59:59	cloudcabinarts.com	webmail.cloudcabinarts.com	C=US, ST=TX, L=Houston, O="cPanel, Inc.", CN="cPanel, Inc. Certification Authority"
2018-06-12T10:54:23.337	2018-06-12T09:54:23	2018-09-10T09:54:23	mail.cloudcabinarts.com	webmail.cloudcabinarts.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2018-06-12T10:54:23.112	2018-06-12T09:54:23	2018-09-10T09:54:23	mail.cloudcabinarts.com	webmail.cloudcabinarts.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3