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

Results forspam.mail.marketmatrix.com

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2025-08-02T12:58:48.807	2025-08-02T00:00:00	2026-08-01T23:59:59	spam.mail.marketmatrix.com	spam.mail.marketmatrix.com	C=US, O=DigiCert Inc, OU=www.digicert.com, CN=Encryption Everywhere DV TLS CA - G2
2025-08-02T12:58:36.317	2025-08-02T00:00:00	2026-08-01T23:59:59	spam.mail.marketmatrix.com	spam.mail.marketmatrix.com	C=US, O=DigiCert Inc, OU=www.digicert.com, CN=Encryption Everywhere DV TLS CA - G2
2021-01-29T12:33:25.064	2021-01-29T00:00:00	2022-01-29T23:59:59	spam.mail.marketmatrix.com	spam.mail.marketmatrix.com	C=US, O=DigiCert Inc, OU=www.digicert.com, CN=Encryption Everywhere DV TLS CA - G1