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

Results forwebmail.io2.com

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2023-09-17T04:54:26.48	2023-09-17T03:54:25	2023-12-16T03:54:24	io2.com	*.io2.com	C=US, O=Let's Encrypt, CN=E1
2023-09-17T04:54:26.201	2023-09-17T03:54:25	2023-12-16T03:54:24	io2.com	*.io2.com	C=US, O=Let's Encrypt, CN=E1
2022-04-06T00:59:43.413	2021-07-29T00:00:00	2022-07-29T23:59:59	io2.com	*.io2.com	C=US, O=DigiCert Inc, OU=www.digicert.com, CN=Encryption Everywhere DV TLS CA - G1
2021-07-29T10:50:51.549	2021-07-29T00:00:00	2022-07-29T23:59:59	io2.com	*.io2.com	C=US, O=DigiCert Inc, OU=www.digicert.com, CN=Encryption Everywhere DV TLS CA - G1
2020-12-09T02:29:17.002	2020-12-09T00:00:00	2021-03-09T23:59:59	io2.com	webmail.io2.com	C=US, ST=TX, L=Houston, O="cPanel, Inc.", CN="cPanel, Inc. Certification Authority"
2020-12-09T02:29:14.242	2020-12-09T00:00:00	2021-03-09T23:59:59	io2.com	webmail.io2.com	C=US, ST=TX, L=Houston, O="cPanel, Inc.", CN="cPanel, Inc. Certification Authority"