ISPs and the anti-spam community view spam complaints as their top source for identifying spammers. Most commonly used email clients now have a “Report spam” button easily accessed by subscribers. When a subscriber receives a message and identifies it as “spam,” he or she can press the spam complaint button and log it with their ISP. These spam complaints can be logged at the ISP level or also relayed back to the original sender by way of feedback loops. Eichner at Pivotal Veracity views these spam complaints as “votes” that email recipients can use to vote “for” or “against” a sender’s reputation.
Because ISPs do not collect intent of a spam complaint, subscribers marking a spam complaint as a way of unsubscribing aggregate with the true spam complaints. Due to this common practice of unsubscribing via spam complaints (in AOL, for example), ISPs have set their spam complaint threshold to allow for some level of false positive spam complaints. However, high spam complaints by originally opt-in subscribers can be a result of sending irrelevant messaging, or sending too frequently. After reviewing what “engagement” is with respect to your email campaigns (e.g., opens or clicks in the past 90 days), a reengagement strategy aimed toward those subscribers without opens and/or clicks will ensure that your audience is less likely to complain that your message is spam.