DKIM adds a digital signature to your emails, allowing the recipient's server to verify that the email was not altered during transmission. To add a DKIM record:
Generate a DKIM key pair (public and private keys) using your email service provider. Log in to your domain registrar's account. Navigate to the DNS settings section. Create a new TXT record. The name will typically be something like default._domainkey and the value will be your DKIM public key. Save the changes and allow some time for the DNS to propagate.