II0-001 · Question #154
In context to email headers, reverse DNS is used to verify
The correct answer is A. Sending machine name. Reverse DNS (rDNS) lookup verifies that the sending machine's IP address maps back to the hostname claimed in the email's SMTP handshake (the HELO/EHLO command), confirming the originating server is who it says it is - making A correct. The receiving machine (B) doesn't need…
Question
In context to email headers, reverse DNS is used to verify
Options
- ASending machine name
- BReceiving machine name
- CFrom address
- DRecipients
How the community answered
(26 responses)- A85% (22)
- B8% (2)
- C4% (1)
- D4% (1)
Explanation
Reverse DNS (rDNS) lookup verifies that the sending machine's IP address maps back to the hostname claimed in the email's SMTP handshake (the HELO/EHLO command), confirming the originating server is who it says it is - making A correct. The receiving machine (B) doesn't need verification via rDNS because the receiver is the one performing the lookup. The From address (C) is a user-visible header field verified by different mechanisms like SPF/DKIM, not rDNS. Recipients (D) are destination addresses and have no relationship to DNS-based sender authentication.
Memory tip: Think "reverse = backwards trace" - rDNS goes backward from IP to hostname to confirm the source (sender's machine), not anything about the destination or the envelope addresses.
Community Discussion
No community discussion yet for this question.