Why are TXT records used for email authentication?

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Review My Emails · Accepted Answer

TXT records became the authentication standard for practical reasons:

Universal support: All DNS providers and resolvers handle TXT records. No compatibility issues.

Flexibility: TXT can hold any text format. New protocols do not require DNS changes.

No new record types: Creating new DNS record types requires global coordination. TXT works immediately.

Precedent: SPF started with TXT. Other protocols followed the pattern.

Theoretically, dedicated record types (like the proposed SPF record type) could be more efficient. Practically, TXT works everywhere and is here to stay.

Using the universal form rather than creating a new form type for each credential. Simpler for everyone.