This also came up for one of our users today. Because the emails are generated from a system that isn't within the org(we're cloud) our users, who have repeatedly been trained on phishing, this it is spam. It would be nice if we could(maybe we can) changed the from name and send address! Looks there's also an idea in this vein too: A change in approach to email notifications
You can raise a case with support to get the from name and/or send address of the emails generated by Jive changed.