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

Results forwebmail.buenbyte.com

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2019-11-28T18:21:21.498	2019-11-28T17:21:21	2020-02-26T17:21:21	buenbyte.com	*.buenbyte.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2019-11-28T18:21:21.256	2019-11-28T17:21:21	2020-02-26T17:21:21	buenbyte.com	*.buenbyte.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2019-05-16T01:35:38.864	2019-05-16T00:00:00	2019-08-14T23:59:59	buenbyte.com	webmail.buenbyte.com	C=US, ST=TX, L=Houston, O="cPanel, Inc.", CN="cPanel, Inc. Certification Authority"
2019-05-16T01:35:19.483	2019-05-16T00:00:00	2019-08-14T23:59:59	buenbyte.com	webmail.buenbyte.com	C=US, ST=TX, L=Houston, O="cPanel, Inc.", CN="cPanel, Inc. Certification Authority"
2018-12-05T01:35:42.969	2018-12-05T00:00:00	2019-03-05T23:59:59	buenbyte.com	webmail.buenbyte.com	C=US, ST=TX, L=Houston, O="cPanel, Inc.", CN="cPanel, Inc. Certification Authority"
2018-12-05T01:35:23.815	2018-12-05T00:00:00	2019-03-05T23:59:59	buenbyte.com	webmail.buenbyte.com	C=US, ST=TX, L=Houston, O="cPanel, Inc.", CN="cPanel, Inc. Certification Authority"
2018-09-20T01:37:27.288	2018-09-20T00:00:00	2018-12-19T23:59:59	buenbyte.com	webmail.buenbyte.com	C=US, ST=TX, L=Houston, O="cPanel, Inc.", CN="cPanel, Inc. Certification Authority"
2018-09-20T01:37:07.377	2018-09-20T00:00:00	2018-12-19T23:59:59	buenbyte.com	webmail.buenbyte.com	C=US, ST=TX, L=Houston, O="cPanel, Inc.", CN="cPanel, Inc. Certification Authority"