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

Results forwebmail.synergee.org

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2021-07-31T03:24:52.721	2021-07-31T00:00:00	2021-10-29T23:59:59	synergee.org	webmail.synergee.org	C=US, ST=TX, L=Houston, O="cPanel, Inc.", CN="cPanel, Inc. Certification Authority"
2021-07-31T03:24:51.503	2021-07-31T00:00:00	2021-10-29T23:59:59	synergee.org	webmail.synergee.org	C=US, ST=TX, L=Houston, O="cPanel, Inc.", CN="cPanel, Inc. Certification Authority"
2021-07-31T03:16:06.115	2021-07-31T00:00:00	2021-10-29T23:59:59	synergee.org	webmail.synergee.org	C=US, ST=TX, L=Houston, O="cPanel, Inc.", CN="cPanel, Inc. Certification Authority"
2021-07-31T03:16:05.63	2021-07-31T00:00:00	2021-10-29T23:59:59	synergee.org	webmail.synergee.org	C=US, ST=TX, L=Houston, O="cPanel, Inc.", CN="cPanel, Inc. Certification Authority"