TXT record
Free-form text on a name. SPF, DKIM, and DMARC live here. So does a lot of vendor noise.
TXT holds arbitrary text. Mail authentication publishes SPF, DKIM public keys, and DMARC policy as TXT. Vendors also dump verification tokens into TXT.
Too many TXT strings, or huge ones, break some resolvers and some mail checks. Read the tags; do not assume every TXT is SPF. See also DMARC (/knowledge/dmarc).
See also: DMARC, DKIM, and SPF, DNS.