This is my perspective alone and isn't meant to sway anyone's opinion, this is just my experience as it's been. Having owned and run my own mail servers myself for some 10 years, I'll tell you something for nothing. Owning your own mail server is not something that comes for free. At least, it wasn't for me. Unless your product has brought something that's drastically different in terms of software, security and spam…
I've been up and running with Helm for the past month on my garrytan.com email domain and it's been zero maintenance.