SendGrid does automatically suppress any spam complaint address reported through traditional feedback loops. However, some webmail providers, notably Gmail, do not provide a traditional feedback loop out of privacy concerns. Rather, they provide an anonymous, aggregate report directly to us about concerning senders.
This matters to you because senders with high spam complaints will often see their mail broadly throttled or blocked during future email campaigns if this remains an unresolved issue. Since Gmail's reporting is anonymous, you won't know specifically who flagged your mail as spam, and you likely won't know this is an issue until SendGrid reaches out to you.
If you receive a report from us about Google spam complaints, or even from traditional feedback loops, we have a few best practices to help you resolve the issue:
If you receive a report from us about spam complaints, use this as an opportunity to implement better list acquisition and maintenance.