You could install a hypervisor like Proxmox on this server. Then you could run separate VMs for Mailcow, your websites and for a reverse proxy.
Maverickz I have a hard time believing that Windows can easily run both a mail and web server and Linux can’t.
Sure it can be done on Linux in general. But Mailcow is designed as an appliance and if you start to mess with it’s fundamental configuration you’re in unsupported teretory. I’m not saying it can’t be done, and no offense, but if you’re not able to figure it out yourself, you will most likely also not be able to fix any issues that it may cause further down the road. So that and potential security issues, is why I would recommend to use the product as it is intended.