WordPress installations are not sending emails - need fully-qualified hostname

The configuration of a FQDN is likely considered to be the responsibility of the host and/or VM provider. For instance, every time I spin up a new VM, it already has a FQDN, due to the way my VM provider has configured the VM images to work. I have found this to be true on two different VM providers, but not true when I spin up a VM on my own hardware