Urgent: Email Deliverability & DNS Issues Fix

I'm facing serious issues with email deliverability and email setup. They are simply not reaching their intended recipients or unable to setup Outlook correctly. The email service in use is IMAP/SMTP, running on a WHM server with Cloudflare DNS.

I need an experienced technician to:
- Audit the current setup
- Diagnose and fix the issues
- Provide advice on optimal configurations

I am unsure about the specific DNS records that have been configured. Therefore, the ideal candidate should have:
- Extensive experience with WHM server and Cloudflare DNS
- Expert knowledge of DNS configuration and email deliverability
- Ability to communicate technical issues in an understandable way.

A brief will be supplied with more detailed information.