Email Spam Score Improvement

I need help improving the spam score of my Gmail system.

Issues:
- Blacklisted IP address
- Authentication issues (SPF, DKIM, DMARC)

You will need to modify DNS records, so access is necessary.

Ideal Skills & Experience:
- Expertise in email authentication protocols (SPF, DKIM, DMARC)
- Experience with Gmail and DNS management
- Knowledge of IP blacklisting and resolution

Please provide a brief outline of your approach to fix these issues.