Comprehensive and Detailed In-Depth Explanation: An MX (Mail Exchange) record defines which mail servers are responsible for receiving email for a domain. If you want to change or redirect email traffic, the MX record must be updated with the correct server information. * Option B (TXT): Stores text-based info - used for SPF, DKIM, etc. * Option C (SPF): Part of email authentication stored in a TXT record; doesn't redirect traffic. * Option D (CNAME): Alias for another domain name - not used for email routing. CompTIA A+ Core 1 Exam Objective Reference: * Objective 2.4: Compare and contrast common networking hardware.