TXT records are used for various purposes, but in the context of email security and deliverability, they are crucial for implementing SPF, DKIM, and DMARC.
SPF (Sender Policy Framework): An SPF record lists the mail servers authorized to send emails on behalf of your domain. Receiving mail servers check the SPF record to verify if the sending server is permitted. This helps prevent email spoofing, where attackers forge the "From" address. SPF records are published as TXT records.
DKIM (DomainKeys Identified Mail): DKIM adds a digital signature to outgoing emails. This signature is verified by the receiving server using a public key published in a TXT record. DKIM ensures that the email content hasn't been tampered with during transit.
DMARC (Domain-based Message Authentication, Reporting & Conformance): DMARC builds upon SPF and DKIM. A DMARC record (also published as a TXT record) tells receiving mail servers what to do with emails that fail SPF and/or DKIM checks (e.g., quarantine or reject them). It also allows for reporting, so domain owners can see how their emails are being handled.
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A) To specify the IP address of a domain: This is the purpose of A records, not TXT records.
C) To identify the mail servers responsible for a domain: This is the role of MX (Mail Exchange) records, not TXT records.
D) To resolve a domain name to an IP address: This is the role of A (IPv4) or AAAA (IPv6) records.
Adding SPF, DKIM, and DMARC as TXT records protects a domain's reputation and prevents malicious actors from abusing it in phishing attacks.