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

Results forwebmail.ridity.com

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2024-04-13T00:31:51.851	2024-04-12T23:31:51	2024-07-11T23:31:50	webmail.ridity.com	webmail.ridity.com	C=US, O=Let's Encrypt, CN=R3
2024-04-13T00:31:51.551	2024-04-12T23:31:51	2024-07-11T23:31:50	webmail.ridity.com	webmail.ridity.com	C=US, O=Let's Encrypt, CN=R3
2019-10-21T14:11:16.691	2019-10-21T00:00:00	2020-01-19T23:59:59	ridity.com	webmail.ridity.com	C=US, ST=TX, L=Houston, O="cPanel, Inc.", CN="cPanel, Inc. Certification Authority"
2019-10-21T14:10:56.532	2019-10-21T00:00:00	2020-01-19T23:59:59	ridity.com	webmail.ridity.com	C=US, ST=TX, L=Houston, O="cPanel, Inc.", CN="cPanel, Inc. Certification Authority"