SPF can be facilitated on PLUSNET domain names - but I doubt that can be done for FREENET.
However, that is not the real issue here. Specifying SPF rules is not mandatory. In the absence of a SPF specification, the receiving email environment SHOULD ACCEPT the email, not reject it.
Therefore, the villain here is Gmail in their incorrect deposition of making optional functionality mandatory. You might care to ask why does Gmail break international technical standards? Because they are big bully boys?
Superusers are not staff, but they do have a direct line of communication into the business in order to raise issues, concerns and feedback from the community.