Email Deliverability Issues? Check Your Data Quality First

Introduction

You spent weeks on the campaign. The copy is sharp, the design is responsive, and the offer is compelling. You hit send—and the results fall flat.

Your immediate reaction is to blame the "creative" or technical settings. You tweak subject lines, blame the time of day, or question your Email Service Provider (ESP).

Stop doing that.

Deliverability issues are rarely caused by your ESP. The uncomfortable truth is that poor data quality undermines deliverability long before technical warnings appear. You are optimising the furniture while the house is burning down.

Here is why your data, not your settings, is the culprit.

What you blame vs. the reality

When open rates dip, teams investigate the wrong suspects. Here is the disconnect:

ISPs (like Gmail) do not just look at what you send. They look at who you send to. If you hit invalid addresses, they assume you are a spammer. They block you long before your team notices a drop in revenue.

The silent killer: data decay

Data decay isn't an anomaly; it is a biological fact. B2B data decays rapidly as people change jobs.

• Role changes: That marketing@ alias is likely unmonitored.
• Abandoned inboxes: Users migrate from Yahoo to Gmail, leaving old accounts to become spam traps.
• Human error: A single typo (name@gmil.com) creates an invalid record instantly.

As these "bad" records accumulate, they act as dead weight. By the time you see a "Deliverability Warning," the damage to your sender reputation has already happened.

Your metrics are lying to you

You cannot optimise what you cannot trust. If your data is dirty, your KPIs are mathematically wrong.

• Open rates: If 20% of your list is invalid, your open rate looks artificially low because your total "sent" volume includes ghosts.
• Click-Through rates (CTR): You cannot get a click from a typo.
• Inbox placement: If you hit spam traps, your emails are routed to junk folders even for your valid customers.

Martina, the Marketing Director, cannot make strategic decisions based on warped mathematics. You need a clean baseline before you can analyse performance.

Why "quick fixes" fail

When deliverability slides, marketers often panic. They pause sends, reduce volume, or migrate to a new ESP.

These are patches, not cures.

Moving a dirty list to a new ESP is simply moving the problem to a new house. The new ESP will eventually flag you just as the old one did. You are treating the symptom, not the disease.

The fix: data integrity

To solve this permanently, stop viewing "deliverability" as a dark art. View it as a data integrity problem.

1. Clean the decay (The cure) You likely already have bad data rotting in your CRM. Before you send your next campaign, you need a deep clean. Use a list cleaning tool (like CORE) to identify and remove invalid addresses and potential spam traps so your next send lands in the inbox.
2. Verify at the point of entry (The prevention) Cleaning your list once is not enough if you let bad data pour right back in. Stop typos and fake sign-ups before they enter your database. Implement a real-time validation API (like MORE) on your forms to catch errors instantly.
3. Monitor your reputation Don't wait for a blocklist warning. Regular hygiene checks ensure that when a contact bounces or becomes risky, they are removed from your active segments immediately—keeping your sender score high.