Should I go to HR?
I am a leader at a startup. Another leader in a different organization emailed me and cc'd my boss and his boss with false allegations. I did reply to the email stating what he said was false and to provide evidence. He hasn't replied yet. I see this person at meetings and we have to interact about 2hrs a week.
The character of this person is that he undermines people, as I have heard from some employees.
Should I go to HR and forward them the email? Or should I look for another job and lay low?