Fixing authentication errors involves ensuring that your SPF, DKIM, and DMARC records are correctly configured:
For SPF, update your DNS records to include all authorized IP addresses allowed to send emails on behalf of your domain. For DKIM, generate a DKIM key pair and publish the public key in your DNS records. For DMARC, create a DMARC policy and publish it in your DNS records, specifying how to handle emails that fail SPF or DKIM checks.