Unproven, at this time.
There is no reliable proof either way whether these emails are authentic.
At best, these emails fit with established theory - either that Biden was corrupt, or that Russia is trying to interfere in US elections. However, fitting with already-believed theory is not proof.
After Fox passed on the story for ...
Marina Abramović - the performance artist in question - apparently confirmed the authenticity of the dinner invitation to the NYT:
Ms. Abramovic said the “Spirit Cooking” dinner, which had the same name as a book and a performance in which she painted absurd recipes in blood on the walls of an Italian gallery, actually involved her cooking a few simple ...