I have successfully managed to run Mailcow January Update 2022 in an unprivileged LXC container with Proxmox. However, you may need to modify some configurations, such as the maximum number of processes for dovecot docker.
The Docker platform allows developers to package and run applications as containers. A container is an isolated process that runs on a shared operating system, offering a lighter weight alternative to virtual machines. Though containers are not new, they offer a number of benefits — including process isolation and environment standardization — that are growing in importance as more developers use distributed application architectures.