Always fun to do if learning but in production even for personal i would recommend you pay for something like startmail or mailfence and use their custom domain features.
i learned exchange on my own and even had dreams of doing multi tenant exchange until exchange online came and jerked off all over that dream
Check iDRAC or iLO on your servers. They are able to pick up memory and cpu errors on the VMs.
You wouldnt happen to have energy saving features enabled would you?