Sender Policy Framework
SPF is described in RFC 7208 and implemented as a DNS TXT record.
example.biz. 86400 IN TXT "v=spf1 a mx ~all"
Too short a time-to-live (here 86400 seconds) is often taken as an indicator of spammishness. The "biz" tld itself uses 900 seconds, but that can be used to quickly revoke a spammer's domain.
DomainKeys Identified Mail
DKIM is described in RFC 6376 and implemented by a public key in another DNS TXT record. Here is the general gist of very simple possible example.
default._domainkey.example.biz. 86400 IN TXT "v=DKIM1; k=rsa; p=base64encodedpublickey"
See also OpenDKIM.
Domain-based Message Authentication, Reporting, and Conformance
_dmarc.example.biz. 86400 IN TXT "v=DMARC1; p=quarantine"