SPF

SPF (Sender Policy Framework) is one of the three critical email authentication protocols, alongside DKIM and DMARC. It works by publishing a DNS TXT record that lists the IP addresses and mail servers authorized to send email on behalf of your domain. When a receiving mail server gets an email claiming to be from your domain, it checks your SPF record to verify that the sending server is authorized. If the sending server's IP is listed in your SPF record, the email passes SPF authentication. If not, it may be flagged as suspicious or rejected. An SPF record looks like: v=spf1 include:_spf.google.com include:amazonses.com ~all Common issues include exceeding the 10 DNS lookup limit, forgetting to include all sending services, and using -all (hard fail) prematurely. For cold email, make sure your SPF record includes your email provider and any third-party sending services you use.