Email marketing analytics and deliverability
Email marketing metrics that still mean something
The short answer
Treat open rate as a rough deliverability signal, not engagement: Apple Mail Privacy Protection downloads remote content, including tracking pixels, in the background, so many "opens" are machine opens. Judge campaigns on click rate, conversions and revenue per email (tracked with UTM tags), and watch list health: bounces, unsubscribes and spam complaints, keeping Gmail's spam rate below 0.1% and never at 0.3%.
On this page 7 sections
Why opens stopped being reliable
An open is recorded when a tiny image in the email loads. Apple's Mail Privacy Protection (Protect Mail Activity) downloads remote content in the background by default, whether or not the person reads the message, through relays that hide their IP address. For everyone on Apple Mail with it switched on, the pixel fires anyway. Open rates rose, send-time optimisation based on opens got worse, and "opened but didn't click" segments filled with people who never saw the email. Most email platforms now flag or filter suspected machine opens; check how yours labels them.
The metrics, in order of usefulness
| Metric | Formula | What it tells you |
|---|---|---|
| Revenue or leads per email | Attributed revenue (or leads) / emails delivered | Whether the channel pays; needs UTM-tagged links and a key event in GA4 |
| Click rate | Unique clickers / emails delivered | Whether the content earned action |
| Click-to-open rate | Unique clickers / unique opens | Content quality among openers; inflated opens drag it down |
| Unsubscribe rate | Unsubscribes / emails delivered | Relevance and frequency |
| Spam complaint rate | Complaints / emails delivered | The number that damages deliverability fastest |
| Bounce rate | Bounces / emails sent (hard and soft separately) | List quality; hard bounces should be removed at once |
| Open rate | Unique opens / emails delivered | Directional only, and only in comparison with your own history |
Gmail's sender rules are the real benchmark
- Since February 2024, every sender to personal Gmail accounts must set up SPF or DKIM, have valid forward and reverse DNS, use TLS and keep the spam rate in Google Postmaster Tools below 0.3%.
- Bulk senders (more than 5,000 messages a day to Gmail accounts) also need SPF, DKIM and DMARC, a From: domain aligned with SPF or DKIM, and one-click unsubscribe (List-Unsubscribe and List-Unsubscribe-Post headers) plus a visible unsubscribe link.
- Google's target is a spam rate below 0.10%, never reaching 0.30%.
Set up Google Postmaster Tools for your sending domain: it is the only place to see Gmail's own view of your spam rate and reputation.
Measuring revenue from email
- Tag every link with utm_source=newsletter (or your platform), utm_medium=email and a utm_campaign per send. Use the UTM builder; most email platforms can add tags automatically.
- Make sure the action on the site is a GA4 key event (generate_lead or purchase).
- Report key events and revenue by session campaign in GA4, next to the platform's click data.
- Compare revenue per email across sends, not open rate.
Keeping the list healthy
Verify addresses at sign-up or before a big send, remove hard bounces immediately, suppress people who have not clicked in six to twelve months (opens no longer prove they are alive), and never buy lists. Track how the list itself grows with the email list growth rate calculator. For the platforms, see best email marketing analytics tools.
Questions
- Is email open rate still accurate?
- Not on its own. Apple Mail Privacy Protection downloads remote content, including tracking pixels, in the background by default, so opens are recorded for messages nobody read. Use click rate, conversions and revenue per email as the main measures.
- What spam complaint rate is too high?
- Gmail asks all senders to keep the spam rate in Postmaster Tools below 0.3%, with a target below 0.10%. At 0.3% or above, deliverability to Gmail suffers.
- What counts as a bulk sender for Gmail?
- Google defines bulk senders as those sending more than 5,000 messages per day to personal Gmail accounts. They must authenticate with SPF, DKIM and DMARC and offer one-click unsubscribe.
Sources
Next step
Try the email list growth rate calculator
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