Hello,
I have gone through with your project details and can help you to migrate email accounts to new account as per your requirement. I will make sure their won't be any kind of data loss.
I have 6 years of experience in setup and management of different Linux web hosting servers, Cloud Servers, Server Management, DNS, Live Migrations, Server Security, Mailing Servers, Email Servers, SSL, Server Monitoring, etc.
I have a long-time experience in managing complicated hosting environments and have solid skills in live migrations, tuning and performance optimizations over Linux OS.
I would like to have a discussion with you to explain things in better way.
Thanks