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

Results formail.hs.notvalid.com

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2024-07-20T02:47:36.482	2024-07-20T01:47:35	2024-10-18T01:47:34	www.www.mail.hs.notvalid.com	www.www.mail.hs.notvalid.com	C=US, O=Let's Encrypt, CN=R11
2024-07-20T02:47:36.218	2024-07-20T01:47:35	2024-10-18T01:47:34	www.www.mail.hs.notvalid.com	www.www.mail.hs.notvalid.com	C=US, O=Let's Encrypt, CN=R11
2024-07-20T02:46:10.06	2024-07-20T01:46:08	2024-10-18T01:46:07	www.mail.hs.notvalid.com	www.mail.hs.notvalid.com	C=US, O=Let's Encrypt, CN=R11
2024-07-20T02:46:09.371	2024-07-20T01:46:08	2024-10-18T01:46:07	www.mail.hs.notvalid.com	www.mail.hs.notvalid.com	C=US, O=Let's Encrypt, CN=R11
2024-07-20T02:37:03.594	2024-07-20T01:37:03	2024-10-18T01:37:02	mail.hs.notvalid.com	mail.hs.notvalid.com	C=US, O=Let's Encrypt, CN=R10
2024-07-20T02:37:03.294	2024-07-20T01:37:03	2024-10-18T01:37:02	mail.hs.notvalid.com	mail.hs.notvalid.com	C=US, O=Let's Encrypt, CN=R10