SPF does not protect you from a pown smtp server (neither DKIM/DMARC, then SPF is "enough" for self-hosted smtp servers, and does force you to use DNS (the SMTP

SPF does not protect you from a pown smtp server (neither DKIM/DMARC, then SPF is "enough" for self-hosted smtp servers, and does force you to use DNS (the SMTP protocol works without DNS).