Your approved senders list — stops strangers from sending as @yourdomain and protects your business name.
SPF (Sender Policy Framework) is a TXT record listing which mail servers are allowed to send email using your domain name. When a message arrives, the receiver checks: is this server on the list?
Your DNS might include a record starting with v=spf1 followed by approved services (Google, Microsoft, your marketing tool) and ending with -all (strict) or ~all (soft).
SPF does not tell receivers what to do when a message fails. It also breaks if you forward mail incorrectly. Pair SPF with DKIM and DMARC for real protection.
Whoever manages DNS for your domain — often your registrar, IT provider, or email host's setup wizard.
