What are SPF, DKIM, and DMARC, and do I need to configure them?

SPF, DKIM, and DMARC are DNS-based authentication protocols that prove you own the domain and authorize email sending. SPF lists authorized senders; DKIM signs emails cryptographically; DMARC defines domain policy. All three are required for best deliverability. Resend provides the exact records to add to your DNS provider.