Deliverability isn't a one-time setup — it requires ongoing monitoring. This guide covers the tools and metrics that reveal whether your emails are actually reaching the inbox, not just being "sent successfully."
Key Metrics to Track
- Bounce rate — should stay under 2%; anything higher signals list quality problems
- Spam complaint rate — should stay under 0.1%; even small increases warrant investigation
- Open rate — a sudden drop often means emails are landing in spam, not that content became less interesting
- Inbox placement rate — the percentage actually reaching the inbox vs. spam folder
Google Postmaster Tools
Free, and essential if you send meaningful volume to Gmail addresses. It reports:
- Domain and IP reputation as seen by Gmail
- Spam rate based on user reports
- Authentication (SPF/DKIM/DMARC) pass rates
- Delivery errors
Set it up by verifying your sending domain via a DNS TXT record at postmaster.google.com.
Reading DMARC Aggregate Reports
If you configured rua=mailto: in your DMARC record, you'll receive periodic XML reports from major providers showing exactly which sources are sending mail as your domain, and whether they pass authentication. Several free tools can parse these into readable dashboards.
Monitoring Blacklist Status
Check your sending IP regularly against major blacklists (Spamhaus, SORBS, Barracuda) — see How to Check and Remove Your IP from Email Blacklists (RBL).
Checking Bounce Categories
Not all bounces are equal:
| Bounce Type | Meaning | Action |
|---|---|---|
| Hard bounce | Address doesn't exist | Remove immediately |
| Soft bounce | Temporary issue (mailbox full, server down) | Retry a few times, then suppress if persistent |
| Block bounce | Rejected due to reputation/content | Investigate underlying cause urgently |
Setting Up Alerting
Configure your email marketing platform (MailWizz, Mautic, Listmonk) to alert you when bounce or complaint rates exceed a threshold, rather than discovering problems after they've already damaged your reputation.
Seed List Testing
Maintain a small set of test accounts across Gmail, Outlook, and Yahoo. Before major campaigns, send to these accounts first and check whether the email lands in the inbox, spam, or promotions tab.
Common Errors
Postmaster Tools shows no data — you need meaningful sending volume to Gmail addresses before data populates; also confirm domain verification was completed correctly.
Bounce rate looks fine but complaints are rising — investigate content, sending frequency, and whether recipients still recognize/expect your emails.
Best Practices
- Check deliverability metrics after every campaign, not just when problems are suspected
- Act on rising bounce/complaint rates immediately, before they compound
- Use seed list testing before large sends
FAQ
Is a 0% complaint rate realistic?
No — some complaints are normal even for well-run lists; the goal is staying well under provider thresholds (generally under 0.1%), not achieving zero.
Related Articles
- How to Check and Remove Your IP from Email Blacklists (RBL)
- Email Marketing Best Practices & Common Pitfalls to Avoid
- How to Configure SPF, DKIM, and DMARC (Complete Guide)
