Glossary
Spam complaint
A recipient marking your message as spam; the provider may pass it back to you as a complaint.
ValidReach Team · Updated 2026-10-26
In practice
Complaint rates are tracked by mailbox providers, and a high rate hurts delivery quickly. The usual causes are surprise (people did not expect the message) and an unsubscribe link that is hard to find.
Verification and sending
Verification does not stop complaints, since valid mailboxes are the ones that complain. It does remove dead addresses, so your remaining list is the audience that matters.