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

Results forwebmail.slpowers.com

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2017-05-26T20:52:04.1	2016-11-10T20:53:01	2019-11-11T22:02:44	mail.slpowers.com	webmail.slpowers.com	C=US, ST=Arizona, L=Scottsdale, O="Starfield Technologies, Inc.", OU=http://certs.starfieldtech.com/repository/, CN=Starfield Secure Certificate Authority - G2
2013-11-20T11:35:16.777	2013-11-04T21:29:37	2016-11-11T22:02:44	mail.slpowers.com	webmail.slpowers.com	C=US, ST=Arizona, L=Scottsdale, O="Starfield Technologies, Inc.", OU=http://certificates.starfieldtech.com/repository, CN=Starfield Secure Certification Authority, serialNumber=10688435
2013-03-26T11:48:00.521	2010-11-11T22:02:44	2013-11-11T22:02:44	mail.slpowers.com	webmail.slpowers.com	C=US, ST=Arizona, L=Scottsdale, O="Starfield Technologies, Inc.", OU=http://certificates.starfieldtech.com/repository, CN=Starfield Secure Certification Authority, serialNumber=10688435