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

Results forsmtp.detectar.com

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2022-05-19T05:22:09.381	2022-05-19T04:22:08	2022-08-17T04:22:07	detectar.com	*.detectar.com	C=US, O=Let's Encrypt, CN=E1
2022-05-19T05:22:08.984	2022-05-19T04:22:08	2022-08-17T04:22:07	detectar.com	*.detectar.com	C=US, O=Let's Encrypt, CN=E1
2022-02-17T18:09:48.301	2022-02-17T17:09:47	2022-05-18T17:09:46	detectar.com	*.detectar.com	C=US, O=Let's Encrypt, CN=E1
2022-02-17T18:09:47.582	2022-02-17T17:09:47	2022-05-18T17:09:46	detectar.com	*.detectar.com	C=US, O=Let's Encrypt, CN=E1
2021-06-02T23:15:00.436	2021-06-02T22:14:59	2021-08-31T22:14:59	smtp.detectar.com	smtp.detectar.com	C=US, O=Let's Encrypt, CN=R3
2021-06-02T23:15:00.042	2021-06-02T22:14:59	2021-08-31T22:14:59	smtp.detectar.com	smtp.detectar.com	C=US, O=Let's Encrypt, CN=R3