How to Diagnose and Fix Email Deliverability Problems

To check your email deliverability, start with three simple tests. First, send a test email to yourself on Gmail — check if it landed and how it looks. Second, use mail-tester.com to catch authentication errors and blocklist placement. Third, use seedlist tools like GlockApps or Emailconsul to see inbox vs. spam placement across providers. For ongoing monitoring, use your provider’s reporting — for example, Maestra offers an Email Health Report that tracks key deliverability metrics and provides improvement tips.

To see the headers: open your email in Gmail, click the three dots menu, and select "Show original." Look for "PASS" next to SPF, DKIM, and DMARC. If any of them show "FAIL," that’s your first problem to fix.

Go to mail-tester.com, send an email to the address they give you, and check the report.

Mail-Tester catches major issues:

If something critical is wrong, you’ll see it right away in the score and breakdown.

For deeper testing, use seedlist services. These tools send your email to dozens or hundreds of test addresses across different providers and report back: inbox, spam, or missing.

This helps you catch partial spam placement — for example, your emails might land in the inbox on Yahoo but go to spam on Gmail. You won’t see that with a single test address.

Two tools worth trying:

Here are a few recent examples from my work — maybe one of these sounds familiar:

Authentication Misconfiguration

One client suddenly couldn’t reach customers on a major regional email provider. Turned out, their SPF wasn’t passing.

Fix: Their SPF record had too many entries — there’s a hard limit of 10, and they’d accumulated services over time. We identified the issue, explained it, and guided them through consolidating their records.

Bot Registration Problem

A client’s bounce rate spiked with "non-existent address" errors.

Fix: We dug in and found bots were registering fake emails on their site. We flagged the pattern, showed them exactly which addresses were bouncing, and recommended anti-bot protection. Double opt-in also helps prevent this.

False Blocklist Placement

A European client got blocked by a regional provider — flagged as spam even though they were legitimate.

Fix: I reached out to the provider's postmaster team with proof: GDPR compliance confirmation, authentication documentation, and an example email. They acknowledged the false positive and removed the block within 24 hours.

When choosing a provider, think about deliverability upfront. Look for clear analytics and hands-on support.

At Maestra, you can track everything yourself in the Email Health Report, which shows delivery rate, bounce rate, and spam complaints — compared against industry benchmarks.

Your Maestra CSM handles deliverability setup during onboarding: configuring Postmaster and sender signatures (SPF, DKIM, DMARC), warming up your sending domains, and building targeted sending segments. After that, we keep monitoring your email health metrics and step in when something looks off.

Here’s a real example: Furniture Fair came to us with open rates stuck at 17% and serious deliverability problems. Their emails were landing in spam instead of the primary inbox.

Our team fixed the deliverability issues, rebuilt their email templates, and launched new automated flows. Within four months, their open rates jumped from 17% to 46%, bounce rate dropped from 4% to 0.58%, and email now drives 11% of their total revenue.

P. S. It’s also a good idea to review your sending practices from time to time — even if your deliverability is stable. Here’s a good checklist:

What to Do if You Have a High Spam Complaint Rate →