Setting Up Email Server - WHM and Ionos cloud need Help.

Hi everyone, This is my first experience with IoNos Cloud (Centos7 OS)+WHM. I have been trying since yesterday to install my mail server. so I currently have: - a DNS configuration: Done.Figure 2 andFigure 4 (WHM root & CPANEL). - Named. active ,confd and working. Figure 8 but when sending emails I receive emails bouncing error 5.0.0 for certain destinations. Figure 6 for others I do not receive any acknowledgment message (Gmail.) Frozen I really don't know what i m missing but If anyone could help me solve this problem I would be very grateful. Thank you ALL.