I have searched the World wide web and the official AWS documentation for a solution to implement the mTLS over Imap connection in AWS Workmail. Unfortunately, without any luck, I did not find any information. I have spoken with tech support over at AWS, and they did not give me the relevant information.
It seems like they do not support this feature on Workmail, the only place where they do support it is on AWS API Gateway.
I'm really out of options; I'm not very familiar with the AWS environment and would like to know if someone has done this configuration in the past and how it can be done. It does look like a simple thing that many other email servers do support (such as Microsoft Exchange)