Eight Ways to Avoid False Abuse Reports
During an email campaign, your Internet Service Provider (ISP) will take notice if just a few recipients click on your message to report it as spam.
ISPs continuously monitor their networks for "abuse" reports, and if your company brings up even a few, they will block you from sending email from their servers. It's a classic case of "guilty until proven innocent", and often results from users who simply hit the spam button to unsubscribe.