I've a modest knowledge of windows, linux, mostly ubuntu gained over more years than I care to remember. I've moved to nethserver from an ancient windows server and equally ancient free mail server at least well protected by Smoothwall and, more recently, PfSense firewall routers. It has at least been a very reliable installation but now way to old, even behind a locked down firewall. The nethserver is set up in AD domain controller mode and will be used as just a mail server and file server.