To implement authentication checks, follow these steps:
Set up an SPF record: Add a TXT record to your domain's DNS settings with the list of authorized IP addresses. Configure DKIM: Generate a pair of cryptographic keys (private and public). Add the public key to your DNS records and configure your email server to sign outgoing emails with the private key. Publish a DMARC policy: Add a TXT record to your DNS settings with your DMARC policy, specifying how to handle unauthenticated emails and where to send reports.