MX record
Also: mail exchanger record
A DNS record that names the mail servers responsible for accepting email for a domain, which is the first thing a sending server looks up under RFC 5321.
An MX record shows that a domain routes mail somewhere and usually reveals the provider, such as Google Workspace or Microsoft 365. It says nothing about whether any particular mailbox exists, and a domain with no MX record can still receive mail through an implicit MX pointing at the domain itself.