Best Practices for Cleaning Lists

Verifying your email list is only the first step. The real impact comes from how you use those results.
By cleaning your list based on Mailerio’s verification data, you protect your sender reputation, maintain high deliverability, and improve engagement metrics.

Why List Cleaning Matters

Unverified or outdated emails can cause:

• Hard bounces, damaging sender reputation
• Spam traps and blacklisting risks
• Low open and click rates
• Blocked or throttled sends by ESPs

Consistently cleaning your lists with Mailerio ensures you only contact real, active, and safe addresses, keeping your campaigns effective and compliant.

Step 1: Analyze Verification Results

Mailerio provides detailed results for each verified address. The most important fields to consider when cleaning your list are:

Step 2: Define Your Cleaning Logic

Depending on your goals, you can apply different filters.

For Business (B2B) Campaigns

• Keep:
  • status = deliverable
  • free = false
  • disposable = false
  • score ≥ 70
• Remove or flag:
  • role = true
  • risky = true
  • unknown and undeliverable

For Marketing or Newsletter Lists

• Keep:
  • status = deliverable or risky with score ≥ 60
  • disposable = false
• Remove:
  • undeliverable, unknown, and duplicates

For User Signups / CRM Imports

• Validate in real time using the API.
• Block disposable, invalid, or risky emails at signup.
• Flag borderline addresses for review or re-verification.

Step 3: Segment Your Lists

Segmentation helps you balance deliverability and reach:

Tip: Keep a “quarantine list” for borderline emails you may want to reverify later.

Step 4: Reverify Regularly

Email data decays quickly even valid addresses can become undeliverable within months.

• Reverify lists every 3–6 months, especially before major campaigns.
• Use Mailerio’s Bulk Verification for existing lists and API verification for new signups.
• Automatically remove or flag addresses that change status to undeliverable.

Step 5: Track Deliverability Metrics

After cleaning, monitor your email performance:

• Bounce rate: Should stay under 2%.
• Spam complaints: Should remain very low (<0.1%).
• Open and click rates: Should rise as your list quality improves.

If bounce rates spike, reverify the affected segment to identify decayed addresses.

Step 6: Maintain Good Sending Practices

Even with a clean list, deliverability depends on how you send emails:

• Warm up new IPs or domains gradually.
• Avoid sudden spikes in sending volume.
• Keep your content relevant, personalized, and compliant.
• Remove inactive subscribers regularly.
• Use verified sending domains (SPF, DKIM, DMARC).

Automation Tips

• Integrate Mailerio’s API directly with your CRM, ESP, or signup form.
• Use webhooks or scheduled tasks to verify new signups automatically.
• Combine results with your own logic:
  • Reject signups if status != deliverable
  • Allow but flag if score ≥ 60 && < 80
  • Auto-block disposable = true

Summary

By following these best practices (check for a more detailed deliverability guide here), you’ll maintain a healthy sender reputation, achieve higher inbox placement, and build a more responsive audience, all while saving credits and reducing waste.