What is a TXT (Text) record used for in email? (SPF, DKIM, DMARC, BIMI)

TXT records are the workhorse of email authentication:

SPF: Published at your domain. Lists IP addresses and servers authorized to send mail for you.

DKIM: Published at selector._domainkey.domain. Contains the public key to verify message signatures.

DMARC: Published at _dmarc.domain. Specifies how receivers should handle authentication failures and where to send reports.

BIMI: Published at default._bimi.domain. Points to your verified logo for inbox display.

All four use TXT records because of their flexibility and universal DNS support.

Different certificates and credentials, all stored in the same type of registry form.