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

Results forwebmail.speed2.squarestack.com

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2020-08-10T23:09:45.816	2020-08-10T22:09:45	2020-11-08T22:09:45	speed2.squarestack.com	*.speed2.squarestack.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-08-10T23:09:45.625	2020-08-10T22:09:45	2020-11-08T22:09:45	speed2.squarestack.com	*.speed2.squarestack.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-08-10T19:50:48.333	2020-08-10T18:50:48	2020-11-08T18:50:48	speed2.squarestack.com	webmail.speed2.squarestack.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-08-10T19:50:48.13	2020-08-10T18:50:48	2020-11-08T18:50:48	speed2.squarestack.com	webmail.speed2.squarestack.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-08-04T23:21:51.713	2020-08-04T22:21:51	2020-11-02T22:21:51	speed2.squarestack.com	*.speed2.squarestack.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-08-04T23:21:51.43	2020-08-04T22:21:51	2020-11-02T22:21:51	speed2.squarestack.com	*.speed2.squarestack.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3