The ratio of unique spam complaints you receive from an email campaign to the number of emails that were delivered in the same campaign is termed as Complaint Rate. Recipients have the option to label your email as ‘This is Junk/Spam.’

The ratio of unique spam complaints you receive from an email campaign to the number of emails that were delivered in the same campaign is termed as Complaint Rate. Recipients have the option to label your email as ‘This is Junk/Spam.’