With over a decade of experience as a senior Linux/Windows system administrator, including expertise in managing servers with WHM and rodcube, I am confident I have the skills necessary to solve the email problem you're encountering. I have an extensive background in troubleshooting and resolving server-related issues, including mail servers. Having worked on both LAMP installations on Linux and IIS, SQL, FTP, and SMTP services on Windows servers, I bring a comprehensive understanding of server environments that extends to the specific challenges you're facing.
Throughout my career, I've demonstrated proficiency in optimizing services such as Apache, MySQL, Nginx, PHP and have effectively addressed spamming activities and managed disk space/storage - all tasks that are crucial for ensuring smooth email functionality. Additionally, my experience with multiple control panels such as cPanel and Plesk aligns perfectly with your use of WHM.
Moreover, my cloud engineering experience, especially with AWS's RDS instances and troubleshooting usages like yours by upgrading them from version2 to version3 without downtime or data loss have equipped me with critical problem-solving abilities even in challenging situations. Hence, I can guarantee a timely and effective resolution of your email problem while prioritizing the security and integrity of your data.