Spam report rate is a metric provided by Internet Service Providers that lets us implement a Feedback Loop (FBL) with them. Not all providers do so. Gmail, for instance, do not offer such a service, but Yahoo and Hotmail, on the other hand, do.
We usually consider anything below 0.1% spam report rate as acceptable. If you go above that threshold, we might temporarily block your account and ask you to improve your deliverability practices before reopening it. Repeated or severe spam report rate issues can lead to an immediate termination of your account.