Deliverability KPIs to Track: Thresholds, Cadence and Tools
6 KPIs that catch deliverability problems before campaign performance drops. Thresholds, monitoring cadence, and tools that surface each signal automatically.
TL;DR
6 KPIs, thresholds, and cadence: the short version
Most deliverability problems are invisible until performance has already declined. The six KPIs below give you early warning before bounce rates spike, domain reputation drops, or your domain hits a blacklist.
6 core KPIs with safe, warning, and critical thresholds; leading vs lagging indicator types; and per-KPI monitoring cadence. Includes examples across Gmail, Outlook, and other ISPs, plus tool recommendations for automated tracking.
KPI Reference
The 6 deliverability KPIs with thresholds at a glance
| KPI | Safe range | Warning threshold | Critical threshold | Type |
|---|---|---|---|---|
| Hard bounce rate | Below 2% | 2% to 5% | Above 5% | Lagging |
| Spam complaint rate | Below 0.08% | 0.08% to 0.1% | Above 0.3% | Leading |
| Inbox placement rate | Above 90% | 80% to 90% | Below 80% | Leading |
| Domain reputation score | High (Google Postmaster) | Medium | Low or Bad | Leading |
| Blacklist status | Zero listings | Minor list (1 listing) | Major list (Spamhaus, Barracuda) | Lagging |
| Authentication pass rate | 100% SPF + DKIM pass | Any DKIM failures | DMARC failures on volume sends | Lagging |
Leading indicators change before campaign performance drops: inbox placement rate and domain reputation are the two to track continuously. Lagging indicators confirm damage that already occurred; both types are required.
Leading Indicators
Inbox placement and domain reputation: 2 KPIs that predict problems before open rates fall
Inbox placement rate measures the percentage of emails landing in the primary inbox across ISPs. A drop here is the first visible sign of reputation drift, appearing days before a bounce spike or blacklist event.
Domain reputation in Google Postmaster sits at four levels: High, Medium, Low, or Bad. A drop from High to Medium warrants investigation. Low means Gmail is actively filtering your mail.
Google's action threshold is 0.10%, enforcement at 0.30%, both calculated against delivered mail. 4 complaints on a 1,000-contact campaign equals 0.40%: already above enforcement. Monitor per campaign and per domain in Google Postmaster.
Lagging Indicators and Cadence
Bounce rate above 2%, blacklists, and auth failures: 3 lagging KPIs and how often to check them
Hard bounce rate above 2% signals list hygiene issues. Above 5%, ISPs throttle your sending domain. Fix starts before the campaign: verify lists before upload, not after bounce rates appear.
Most teams check blacklist status reactively, after a campaign fails. Automated monitoring across 50+ lists catches a listing within hours instead of days.
| Cadence | KPIs to check |
|---|---|
| Daily (automated) | Blacklist status (50+ lists), spam placement alerts |
| Weekly (manual) | Domain reputation (Postmaster), inbox placement rate, DMARC auth pass rate |
| Per campaign | Hard bounce rate, spam complaint rate (within 48h of send) |
That cadence is too slow. Reputation damage compounds faster than monthly reviews can catch it.
Recommended Tools
7 tools that surface deliverability KPI signals automatically
Two tool types cover a complete monitoring setup: placement testing tools for leading indicators, and verification tools that prevent lagging indicator problems. Most teams use one from each group.
Common Questions
6 deliverability KPI questions answered
Keep hard bounce rate below 2% per campaign. Above 5%, ISPs throttle your sending domain: verify lists before every upload with ZeroBounce or Bouncer to remove invalid and high-risk addresses.
Go to postmaster.google.com, add your sending domain, and verify via a DNS TXT record. Domain reputation (High/Medium/Low/Bad) populates once you reach sufficient Gmail sending volume; GlockApps integrates directly for extended storage and automated alerts.
Inbox placement rate measures where emails land: primary inbox, spam, or promotions. Open rate only counts opens among emails that reached the inbox, so a drop in opens often means placement dropped first.
Run a placement test before every new campaign and again 7 days after launch. For ongoing monitoring, MailReach or GlockApps automate continuous testing without manual effort.
Google's action threshold is 0.10%, enforcement at 0.30%, both calculated against delivered mail. Monitor complaint rates per campaign in Google Postmaster to catch spikes before they accumulate across sending domains.
Authentication is a prerequisite: without SPF and DKIM, DMARC reports inflate failure metrics and Google Postmaster cannot attribute reputation to your domain accurately. See the SPF/DKIM/DMARC Setup Guide for full configuration steps.
KPIs identified. Next: build the pre-send checklist that protects them.
The full deliverability checklist organizes these KPIs into a step-by-step pre-launch workflow for every domain and campaign.