Why do email services rely heavily on TXT records?

TXT records became the standard for email authentication because:

Flexibility: TXT records can hold any text content. No new record type needed for each protocol.

Universal support: All DNS providers support TXT records.

Backward compatibility: Adding new authentication methods does not require DNS protocol changes.

SPF: Lists authorized sending IPs in a TXT record.

DKIM: Publishes public keys in TXT records at selector._domainkey.domain.

DMARC: Defines policies in a TXT record at _dmarc.domain.

TXT records are the Swiss Army knife of DNS for email authentication.

The universal form in the harbor registry. Adaptable to any certification requirement.