From the video:
“Most Internet service providers won’t let you run your own servers [at home]”
This brings up a deeper issue than the idea of running your own mail server; it can probably be lumped into the broader net neutrality discussion, but I digress.
I echo @2disbetter and their concerns; in addition, all your Helm traffic is designed to funnel through Helm cloud servers anyway, so… what are you even gaining here?
If you administer through a mobile app, I also worry about yet another system on my network that broadens my attack surface without access to updating / logging / forensics on the core OS.