I am good at server and desktop virtualization, I have setup kvm virtualization for my company running for almost 4 years, without any problem, completely opensource, I confirure open source raspberry thinclient my own, 100% open source either, our company now I am working on, all use this client now, I can write c# winform problem, I wrote send sms software, I am good at VPN configure also, site-to-site and client-to-site type. also windows server and linux server configure, I configure my own mail server centos + postfix + mysql + dovecot + postadmin, now I send mail use my own mail server for almost 5 years, nothing problem, my mail server have a 10 store on mail-tester website.