Recipient Shield protects your sender reputation and prevents security threats by automatically rejecting emails to high-risk recipient addresses. This proactive security feature filters out toxic domains, temporary email addresses, and domains with common typos before messages are sent.
Sender Protection: Recipient Shield helps maintain your sender reputation by preventing emails to known problematic domains that could damage your deliverability scores.

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Why Use Recipient Shield?

Your sender reputation directly impacts email deliverability. Sending to toxic, temporary, or typo-squatted domains can:
  • Damage sender reputation through high bounce rates and spam complaints
  • Waste resources on invalid or temporary recipients
  • Enable fraud by allowing bad actors to create fake accounts
  • Expose users to attacks through typo-squatted domains used for phishing

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Protection Types

Recipient Shield provides two distinct protection mechanisms:

Toxic & Tempmail Filtering

200,000+ blocked domainsAutomatically reject emails to known toxic and temporary email domains

Typo Detection

Common misspellings blockedPrevent delivery to typo-squatted domains that attackers use for phishing

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Toxic & Temporary Email Filtering

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What Are Toxic Domains?

Toxic domains are email domains with low reputation scores that are frequently used by bad actors for:
  • Phishing attacks to steal user credentials
  • Spam campaigns that damage sender reputation
  • Account takeover attempts and other malicious activities
  • Fraud and abuse of trial offers and promotional codes

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What Are Temporary Email Domains?

Temporary email (tempmail) services provide disposable email addresses that users leverage to:
  • Bypass trial limitations by creating multiple accounts
  • Generate fake accounts on your platform
  • Avoid legitimate communications from your service
  • Abuse promotional offers and discount codes

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How It Works

When toxic and tempmail filtering is enabled:
  1. Pre-send validation: AhaSend checks each recipient domain against our database of 200,000+ known toxic and temporary email domains
  2. Automatic rejection: Matching domains are immediately rejected
  3. Error response: Your application receives a clear error message
  4. Real-time updates: Our blocklist is continuously updated with newly identified toxic domains
Database Updates: Our toxic domain database is continuously updated based on threat intelligence from multiple sources, ensuring protection against emerging threats.

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Rejection Response

When an email is blocked due to toxic or tempmail domain: 
553 Requested action not taken: recipient domain is toxic or tempmail
This error is returned via:
  • SMTP: During the RCPT TO command
  • API: In the response body with appropriate HTTP status code

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Typo Detection & Prevention

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The Typo-Squatting Threat

People make typing mistakes. They enter gmil.com instead of gmail.com or outlok.com instead of outlook.com. Attackers exploit these mistakes by:
  1. Registering misspelled domains of popular email providers
  2. Accepting all incoming emails to these domains
  3. Harvesting sensitive information from misdirected emails
  4. Using collected data for targeted phishing attacks

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How Typo Detection Works

When typo detection is enabled:
  1. Pattern matching: AhaSend identifies common misspellings of major email providers
  2. Domain verification: Checks if the recipient domain matches known typo patterns
  3. Automatic blocking: Prevents delivery to detected typo domains
  4. User protection: Shields your users from potential security threats

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Common Typo Examples

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Rejection Response

When an email is blocked due to domain typo: 
553 Requested action not taken: recipient domain has common a typo
User Experience: Consider implementing client-side typo detection in your signup forms to catch these errors before submission, providing a better user experience while maintaining security.

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Enabling Recipient Shield

Access Security Settings

Navigate to your account security options:
  1. Log in to your AhaSend dashboard
  2. Go to Account Settings from the main menu
  3. Click the Security tab in the sidebar

Configure Toxic Domain Filtering

Enable toxic and tempmail domain protection:
  1. Locate “Toxic & Tempmail Domain Filtering” section
  2. Toggle the feature to “Enabled”
  3. Review the description to understand the protection scope
This will immediately begin blocking emails to our database of 200,000+ known toxic and temporary email domains.

Configure Typo Detection

Enable typo-squatting protection:
  1. Locate “Domain Typo Detection” section
  2. Toggle the feature to “Enabled”
  3. Review the common typo patterns that will be blocked
Ensure your legitimate recipient domains don’t match typo patterns before enabling this feature.

Save Configuration

Apply your security settings:
  1. Click “Save Settings” at the bottom of the page
  2. Wait for confirmation message
  3. Test with a known toxic domain to verify activation
Settings take effect immediately across all sending methods (SMTP and API).

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Implementation Considerations

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Handling Rejections in Your Application

When Recipient Shield blocks an email, your application should: 
import smtplib
from email.mime.text import MIMEText

def send_email(recipient):
    try:
        # Your SMTP sending code
        server.send_message(msg)
    except smtplib.SMTPRecipientsRefused as e:
        error_message = str(e.recipients[recipient][1])

        if "toxic or tempmail" in error_message:
            # Handle toxic domain rejection
            log_toxic_domain_attempt(recipient)
            return "Invalid email domain. Please use a permanent email address."

        elif "common a typo" in error_message:
            # Handle typo detection
            suggested = suggest_correction(recipient)
            return f"Email domain appears to have a typo. Did you mean {suggested}?"

        else:
            # Handle other SMTP errors
            raise

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User Experience Best Practices

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Benefits

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Security Advantages

Reputation Protection

Maintain high sender scores by avoiding problematic domains that generate bounces and complaints

Fraud Prevention

Block fake account creation and trial abuse using temporary email addresses

User Safety

Protect users from accidentally sending sensitive information to typo-squatted domains

Resource Optimization

Save sending resources by filtering invalid recipients before transmission

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Operational Benefits

  • Reduced bounce rates from invalid or non-existent domains
  • Lower complaint rates by avoiding spam trap domains
  • Improved deliverability through better sender reputation
  • Decreased fraud from temporary email abuse
  • Enhanced security posture against phishing attacks

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Monitoring and Analytics

Track the effectiveness of Recipient Shield through:
  1. Rejection logs: Monitor blocked attempts in your application logs
  2. Pattern analysis: Identify trends in rejected domains
  3. False positive tracking: Review any legitimate domains incorrectly blocked
  4. Security metrics: Measure reduction in fraud and abuse
Regular Review: Periodically review rejection patterns to identify potential attacks or abuse campaigns targeting your service.

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FAQ