[onei]

If you want emails from some random internal machine, you can use one of the HPE SMTP servers. There was one for internal email, another for external iirc although I'm not sure there was a difference in practice. Those SMTP servers would do a DNS lookup before accepting the email.

When I set this sort of thing up, I'd get myself a hostname on an internal subdomain. But that was a truly miserable experience. It was a multi-stage form submission on a server I imagine to be the closest possible relation to an actual potato. It was soul-destroyingly slow. Alternatively, you could just pretend your machine was hpe.com - the hostname was valid, even if the IP was totally wrong, and the SMTP server would accept it.

My guess is that there was a bunch of stuff that pre-dated the HP/HPE split and they took the quick and dirty option whenever the old internal domain name got yanked during the changeover. And if your process runs as root, you get [e-mail] and hope there's something in the subject/body to identify the specific machine.