How does the complaint threshold work?

Any complaints that customers make for a given email are tracked by Mandrill or Sendgrid and imported into MageMail (a complaint is when a customer clicks the Spam button in their email client).

If that number goes over the threshold of 5 per 10,000 emails (the industry standard is 10 per 10,000 emails), the message will be automatically disabled to prevent your sender score from being negatively impacted.