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

Results forwebmail.login.corpseed.com

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2020-02-28T04:00:38.983	2020-02-28T00:00:00	2020-05-28T23:59:59	login.corpseed.com	webmail.login.corpseed.com	C=US, ST=TX, L=Houston, O="cPanel, Inc.", CN="cPanel, Inc. Certification Authority"
2020-02-28T03:59:40.291	2020-02-28T00:00:00	2020-05-28T23:59:59	login.corpseed.com	webmail.login.corpseed.com	C=US, ST=TX, L=Houston, O="cPanel, Inc.", CN="cPanel, Inc. Certification Authority"
2019-12-26T03:21:19.33	2019-12-26T00:00:00	2020-03-25T23:59:59	login.corpseed.com	webmail.login.corpseed.com	C=US, ST=TX, L=Houston, O="cPanel, Inc.", CN="cPanel, Inc. Certification Authority"
2019-12-26T03:20:59.236	2019-12-26T00:00:00	2020-03-25T23:59:59	login.corpseed.com	webmail.login.corpseed.com	C=US, ST=TX, L=Houston, O="cPanel, Inc.", CN="cPanel, Inc. Certification Authority"
2019-10-11T05:33:50.674	2019-10-11T00:00:00	2020-01-09T23:59:59	login.corpseed.com	webmail.login.corpseed.com	C=US, ST=TX, L=Houston, O="cPanel, Inc.", CN="cPanel, Inc. Certification Authority"
2019-10-11T05:33:32.521	2019-10-11T00:00:00	2020-01-09T23:59:59	login.corpseed.com	webmail.login.corpseed.com	C=US, ST=TX, L=Houston, O="cPanel, Inc.", CN="cPanel, Inc. Certification Authority"