Email Deliverability Metrics: The Numbers That Actually Matter
Open rates and click rates tell you about engagement. But delivery rate, inbox placement, spam complaint rate, and bounce rate tell you about deliverability. Here's what to track.
Delivery rate vs inbox placement rate
Delivery rate: The percentage of emails accepted by the receiving server. An email is 'delivered' even if it goes to the spam folder. Typical good delivery rate: 97-99%.
Inbox placement rate (IPR): The percentage of emails that land in the primary inbox (not spam, not promotions). This is the metric that matters for engagement and revenue. Typical good IPR: 90-95%+.
Many senders focus on delivery rate and miss that their inbox placement is terrible. Use inbox placement testing tools (Litmus, Email on Acid, GlockApps) to measure actual inbox vs. spam placement across major providers.
Bounce rate
Bounce rate = (bounced emails / sent emails) × 100
Hard bounce rate: Under 0.5% is acceptable; above 2% is a serious problem. Soft bounce rate: Under 5% is typical; investigate if consistently higher.
Track bounce rates by campaign and by list segment to identify which sources are generating bad addresses. A spike in bounces after importing a new segment means that segment has quality issues.
Spam complaint rate
Spam complaint rate = (spam reports / delivered emails) × 100
Spam complaint rates are notoriously under-reported in ESP dashboards — only providers running feedback loops (FBLs) report complaints back to ESPs. The actual rate may be 10× what your dashboard shows. Monitor directly via Google Postmaster Tools for the most accurate Gmail data.
- 0.10%
- Gmail complaint threshold
- 0.08%
- Yahoo complaint threshold
- 0.30%
- Gmail blocking threshold
- ~10×
- Under-reporting factor
Above this: filtering increases
Required by 2024 bulk sender mandate
Sustained above this: delivery blocked
ESP dashboard vs. actual complaint rate
Open rate (and its limitations)
Open rates measure engagement but have significant limitations post-iOS 15 (Apple Mail Privacy Protection). Apple Mail pre-fetches email content, artificially inflating open rates for Apple Mail users.
More reliable engagement metrics: - Click-to-open rate (CTOR): Clicks / opens — measures content relevance among those who opened - Reply rate: Direct engagement signal not affected by tracking pixel issues - Revenue per email: Ultimate engagement metric for commercial email
Still watch for sudden drops in open rate — even with tracking issues, a significant drop often indicates deliverability problems (shift from inbox to spam).
Deliverability health dashboard
Set up alerts for any metric that crosses a warning threshold so you can respond before a problem becomes a crisis. The table below defines the target, warning, and critical levels for each metric.
Email deliverability benchmark reference — track per campaign
| Metric ↕ | Target (Good) ↕ | Warning ↕ | Critical — Act Immediately ↕ |
|---|---|---|---|
| Delivery rate | > 99% | < 98% | < 95% |
| Hard bounce rate | < 0.5% | > 1% | > 2% |
| Soft bounce rate | < 2% | > 3% | > 5% |
| Spam complaint (Gmail) | < 0.08% | > 0.10% | > 0.30% |
| Spam complaint (Yahoo) | < 0.05% | > 0.08% | > 0.30% |
| Inbox placement rate | > 95% | < 85% | < 70% |
| Domain reputation (Postmaster) | High | Medium | Low or Bad |
| Blacklist listings | 0 | 1 minor list | Spamhaus / Barracuda |
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