The share of delivered emails that recipients marked as spam. Mailbox providers treat it as one of the strongest signals that your mail is unwanted.
Formula
Spam complaint rate = spam complaints ÷ emails delivered × 100
Example
Meera's email is delivered to 8,000 people and 8 mark it as spam. Her spam complaint rate is 8 ÷ 8,000 = 0.1%.
How you'll hear it
“Spam rate in Postmaster Tools crossed 0.3% after that import; stop sending to those addresses now.”
What it helps you decide
Whether to stop sending to a source of addresses, slow down frequency, make the unsubscribe link easier to find, or fix authentication before a big send.
Where people misread it
Your email tool and Gmail may show different numbers: Google's rate in Postmaster Tools is based on Gmail's own data. A low rate across the whole list can hide a high rate in one bad segment.
The story
Before Diwali a supplier offers Meera 3,000 email addresses of 'fashion shoppers in Pune'. She adds them to her festive send.
| Delivered | 8,000 |
| Spam complaints | 8 |
| Spam complaint rate | 0.1% |
|---|
| Delivered | 11,000 |
| Spam complaints | 41 |
| Spam complaint rate | 0.37% |
|---|
The number looks right. 41 complaints out of 11,000 is still under half a percent, and 3,000 more people saw the offer.
What it hides. The 3,000 new addresses alone produced 33 complaints, 1.1%. Google's sender guidelines ask all senders to keep the spam rate below 0.3% and ideally under 0.1%. Crossing that line can push all her mail, including order confirmations, into spam.
What to look at instead. Complaint rate by source and by segment. She removes the bought addresses and checks her rate in Google Postmaster Tools before the next send. Those people never agreed to hear from her, which is also a consent problem under the DPDP Act.
All figures are fictional and illustrative.
Check your spam complaint rate
The example's numbers are filled in. Replace them with yours.
At or below 0.1%, within Google's recommended level. Keep watching it by segment.
Don't confuse it with
- Unsubscribe rate: people leaving politely; a complaint tells the mailbox provider your mail is unwanted.
- Bounce: a delivery failure, not a reader's judgement.
Related terms
Sources
- Email sender guidelines, Google (Gmail Help)
- The Marketer's Guide to Email Deliverability, Litmus, 2025