SPF authenticates the envelope-from domain, while DKIM authenticates the header-from domain. They're both useful, specially coupled with DMARC. DMARC authorize

SPF authenticates the envelope-from domain, while DKIM authenticates the header-from domain. They're both useful, specially coupled with DMARC. DMARC authorizes recipient servers to outright refuse email from your domain if it does not contain a valid DKIM signature, and/or comes from a non-authorized IP. In short, SPF+DKIM+DMARC prevent email spoofing from your domain, protecting you from backscatter and reputation degradation.