Track these per (tenant, destination, day):
| Metric | Warning | Critical |
|---|---|---|
| Delivery rate | <95% | <90% |
| Bounce rate (hard) | >2% | >5% |
| Complaint rate (FBL) | >0.1% | >0.3% |
| Throttle hits (4xx) | >5% | >20% |
| Queue depth per destination | growing | >1h backlog |
| Auth failures (DKIM/DMARC) | >0.1% | >1% |
| Open rate (where measurable) | declining | <10% |
KumoMTA exposes Prometheus metrics on /metrics endpoint (enabled via init.lua HTTP listener). Scrape every 15s.
Sample Grafana panels:
- Stacked bar of delivery vs bounce vs deferred per destination.
- Heatmap of complaint rate per tenant per day.
- Queue depth time series with annotations on shaping changes.
🎯 The metric you should obsess over is complaint rate. Above 0.3% you're in soft-filter territory; above 0.5% you're being blocklisted.
Sign in to keep track of what you have read.