Your dashboard puts bounce rate and complaint rate in adjacent tiles, so you end up treating them as two flavors of the same problem. They measure different events, taken at different moments, by different systems. One can be fine while the other is your incident.
Last verified: 26 September 2026, against Google’s spam-rate definitions, Yahoo’s complaint-rate definition, and the SES enforcement FAQ.
Bounce rate vs complaint rate: two different events
| Bounce rate | Complaint rate | |
|---|---|---|
| When it happens | The receiving server refuses or fails the delivery | A person who received the mail uses a spam or junk control |
| Who is speaking | The mailbox provider’s server | The recipient |
| What a low number proves | Servers are accepting mail | Fewer recipients are objecting |
| What a low number does not prove | The mail reached the inbox | Nobody is deferring or blocking you |
Hard vs soft bounce splits the left column. Spam complaint rate is the right column, including when the list was opted in and people still clicked spam.
What each provider actually publishes
Label these as that provider’s rule. Do not average them into one “dangerous” percentage.
Gmail and Yahoo. Both publish complaint-rate guidance, not bounce quotas. Gmail’s user-reported spam rate and what happens near 0.10% and 0.30% are covered in spam complaint rate. Mail that was rejected never became a spam click, and delivery errors are a separate Postmaster view.
Amazon SES. SES is the provider that publishes both. SES counts hard bounces only, recommends staying under a 2% bounce rate, and can put your account under review at 5%. That 2% is SES’s number, not a rule every mailbox provider enforces. On complaints, SES recommends staying below 0.1%, reviews at 0.1% or greater, and may pause sending at 0.5% or greater. The SES deliverability page covers the enforcement side. You can check your own hard-bounce figure against those lines with the bounce rate calculator.
Klaviyo. In-product bands for bounce and spam are Klaviyo’s warnings inside Klaviyo. They are not the Gmail or SES thresholds. Gmail complaints are not in that tile.
Outlook 550 5.7.515. Microsoft’s article describes an authentication rejection. It does not say the bounce was caused by a complaint percentage.
How to pick the dangerous one this week
If your customers are not getting mail and your log is full of 4xx or 5xx, you are in a bounce or deferral incident even if nobody has complained. Start with why bounce rate jumped.
If your ESP says delivered and your customers say spam, you are in a complaint and placement incident even if bounce rate is under 1%. Start with why mail goes to spam and Postmaster’s spam rate.
If SES warns you and Gmail looks calm, believe both. SES can pause sending on its own bounce or complaint math while Gmail is still accepting other mail. Fix the account SES is measuring. Do not “balance” it against a Gmail chart from a different week.
If you need a business translation after the signal is identified, deliverability ROI uses your revenue and your spam share. Do not turn a bounce rate into that formula. Bounced mail was not a lost open. It was mail the server refused.
InboxEagle
Put a number on your bounce side first
Enter sends and hard bounces and see where you sit against the 2% line SES recommends. Complaints need Postmaster, which is Gmail's complaint view.
Sources
- Email sender guidelines, Google. Spam-rate guidance for bulk senders.
- Postmaster Tools, Google. Spam rate versus delivery errors.
- Sender best practices, Yahoo. Complaint rate under 0.30% on inbox-delivered mail.
- SES enforcement FAQ, AWS. Separate bounce and complaint review and pause levels.