Tips for Evaluating the Verification Results

1. Introduction

When you use BounceBan (or any similar email verification solution), you receive a status for each email address: typically “Deliverable”, or “Undeliverable”. These statuses indicate whether emails sent to these addresses are expected to go through successfully. However, email deliverability can be influenced by various external factors (sending reputation, server configuration, content filters, etc.).

To accurately evaluate verification results and minimize the risk of sending to invalid or problematic addresses, it’s best to do real-world testing of a sample of verified addresses — especially those labeled as Deliverable.

2. Why Real-World Testing Matters

Many factors affect email deliverability, including:

• Sender reputation: If you send emails from an IP address or domain with a poor reputation, otherwise valid addresses may bounce or get filtered.

• Email server settings: Some domain owners might have specialized security settings or filters that reject mail from external, unknown or lower-reputation senders.

• Email content: Heavily promotional or spam-like content can also result in blocked messages.

Real-world testing (i.e., actually sending emails to the verified addresses) helps you confirm whether the Deliverable or Catchall addresses truly accept mail under normal sending conditions.

3. Preparing a Clean Test Environment

1. Use a reliable sender account

• Send your test emails using a reputable business email account, such as a Google Workspace Gmail account.

• Avoid using third-party bulk-sending platforms (e.g., SendGrid, Mailchimp) for these tests, as their IP pools, configurations, and additional reputation factors can skew results.

• Ensure your test account’s domain is in good standing and not associated with spam activities.

2. Send to a reasonably large sample

• Select at least 500 addresses from different domains that BounceBan (or your other verification service) marked as Deliverable.

• This sample size provides a more accurate understanding of your overall list quality and real-world bounce rate.

4. Conducting the Test

1. Draft a simple, neutral email

• Keep the message content simple to reduce the chance of it being flagged as spam.

• Include only text, so that filtering based on content is less likely.

2. Send the messages

• Send your test messages one at a time or in small batches. To protect recipients’ privacy, use BCC instead of listing all email addresses in the To field.

• Monitor the sending process to ensure all intended addresses receive an email.

3. Track the results

• Watch for bounces or Non-Delivery Reports (NDRs).

• Record how many emails resulted in a bounce and the specific bounce messages if available.

5. Evaluating Results & Diagnosing Issues

1. Calculate your bounce rate

• Bounce Rate = (Number of bounced emails) ÷ (Number of emails sent) × 100%

• A bounce rate of 3% or lower is typically acceptable for a healthy, verified list.

• If your bounce rate is higher than 3%, you need to investigate why.

2. Review the bounce messages (NDRs)

• NDRs often include codes or text that explain why the email was not delivered. Common patterns include:

• “Mailbox unavailable” or “User unknown”: Usually indicates the address does not exist (i.e., the verification service might have been incorrect, or the address may have become invalid recently).

• “Your IP/domain is blocked” or “Access denied”: Suggests a reputation issue on the sender’s side, rather than invalid email addresses.

• “Quota exceeded”: The recipient’s mailbox is full (a temporary or “soft bounce”).

• “Message content rejected”: The content (or attachments) triggered spam filters or policy rules.

3. Differentiate invalid addresses from reputation blocks

• If you see a consistent “User unknown” or “No such mailbox” response, it indicates invalid emails.

• If you see “Rejected” or “Blocked by policy” messages for multiple addresses, that likely indicates a sender reputation or content issue, rather than invalid emails.

6. Troubleshooting High Bounce Rates

1. Confirm you used a clean sender domain/account

• If your test email was sent from a domain with poor sending history, your high bounce rate might be partially due to blocks or spam filters.

2. Check your email content

• If the test email has suspicious links or spammy wording, recipients’ servers might reject it.

3. Re-verify addresses

• If the addresses that bounced were marked as valid by BounceBan, try verifying them again to see if they might have changed status or if there was an error.

4. Contact BounceBan support

• If you consistently see invalid or questionable results, provide specific details and bounce message samples to the verification service’s support team for analysis.