Deliverability glossary · Updated 2026-08-10
Spam complaint rate
Spam complaint rate is the share of delivered messages recipients mark as spam. Gmail and Yahoo require bulk senders to stay below 0.3%, with 0.1% the practical working target.
A complaint is the strongest negative signal a recipient can send. Unlike a bounce, which reflects list quality, a complaint reflects the message itself — it was delivered to a real person who decided it was spam.
The 0.3% threshold Gmail and Yahoo published in 2024 sounds forgiving until you convert it: three complaints in a thousand delivered messages. Experienced senders treat 0.1% as the ceiling and investigate anything above it, because complaint rates rise faster than they fall.
Complaints are reported through feedback loops, which most major providers offer and which your sending platform should be subscribed to. Without that subscription you are flying blind — the damage accumulates with no visible symptom until placement collapses.
The most effective reduction is a prominent, functional unsubscribe. Every recipient who opts out cleanly is one who did not press the spam button instead.
How Raechly handles it
Complaint notifications arrive over an SNS-signature-verified SES webhook and are recorded against the lead. Combined with correctly implemented one-click unsubscribe, the intent is to route irritation into opt-outs rather than complaints.
Related terms
One-click unsubscribe
RFC 8058 one-click unsubscribe lets a mailbox provider opt a recipient out with a single POST request, no landing page and no confirmation step.
List-Unsubscribe
List-Unsubscribe is an email header giving mailbox providers a machine-readable way to opt someone out.
Sending reputation
Sending reputation is the trust score mailbox providers assign to your domain and IP based on complaint rate, bounce rate, engagement and authentication history.
Back to the full deliverability glossary, or read how these pieces fit together in how Raechly protects deliverability.