CompTIA A+ Core 1 (220-1201)NetworkingMedium
A mail administrator wants to reduce spam by allowing receiving mail servers to verify that an incoming email's source IP address matches the domain it claims to be from using a reverse lookup. Which DNS record type enables this reverse lookup?
- AA record
- BMX record
- CCNAME record
- DPTR record
Show answer & explanationAnswer & explanation
Correct answer: D. PTR record
A PTR (pointer) record maps an IP address back to a domain name, enabling reverse DNS lookups often used by mail servers to verify sender legitimacy and reduce spam.
Why the other options are wrong
- A. An A record maps a domain name to an IPv4 address (forward lookup), not reverse.
- B. An MX record specifies the mail server responsible for receiving email for a domain.
- C. A CNAME record creates an alias pointing one domain name to another.
PTR Record
A DNS record type used for reverse lookups, mapping an IP address to its associated domain name.
- Opposite of an A record (forward lookup)
- Commonly used for anti-spam email verification
- Stored in the in-addr.arpa reverse DNS zone
Memory trick: PTR 'Points The Reverse' way, IP to name.