Which specific DNS record shows which mail server is in charge of a domain's email?

The specific DNS record that shows which mail server is in charge of a domain's email is the MX record. MX stands for Mail Exchanger. The Domain Name System, or DNS, acts as the internet's phonebook, translating human-readable domain names, such as example.com, into numerical IP addresses that computers use to locate each other. When an email is sent to a recipient, the sender's mail server performs a DNS lookup for the recipient's domain. This lookup specifically queries for the MX records associated with that domain to identify the designated mail servers responsible for handling its email. Each MX record contains two essential pieces of information: a preference value and the domain name of the mail server itself. The preference value, also known as priority, is a number that indicates the order in which mail servers should be contacted. A lower number signifies a higher preference, meaning that email delivery agents will first attempt to connect to the mail server listed with the lowest preference value. If that server is unavailable, they will then try the server with the next lowest preference, and so on. The domain name specified within the MX record's value, for example, mail.example.com, must itself resolve to an IP address via an Address record. An Address record, commonly known as an A record for IPv4 addresses or an AAAA record for IPv6 addresses, maps a domain name directly to its corresponding numerical IP address. This two-step resolution process allows the sending mail server to find the precise IP address of the recipient's mail server, enabling it to establish a connection and deliver the email successfully.