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

Results foremail.costkill.com

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2025-11-10T06:20:21.844	2025-11-10T05:21:51	2026-02-08T05:21:50	email.costkill.com	email.costkill.com	C=US, O=Let's Encrypt, CN=R13
2025-11-10T06:20:21.603	2025-11-10T05:21:51	2026-02-08T05:21:50	email.costkill.com	email.costkill.com	C=US, O=Let's Encrypt, CN=R13
2023-01-17T17:26:01.788	2023-01-17T16:26:01	2023-04-17T16:26:00	costkill.com	*.costkill.com	C=US, O=Let's Encrypt, CN=R3
2023-01-17T17:26:01.552	2023-01-17T16:26:01	2023-04-17T16:26:00	costkill.com	*.costkill.com	C=US, O=Let's Encrypt, CN=R3
2022-11-18T15:27:14.713	2022-11-18T14:27:14	2023-02-16T14:27:13	costkill.com	*.costkill.com	C=US, O=Let's Encrypt, CN=R3
2022-11-18T15:27:14.406	2022-11-18T14:27:14	2023-02-16T14:27:13	costkill.com	*.costkill.com	C=US, O=Let's Encrypt, CN=R3