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Troubleshooting Email Spam Rejection: How to Improve Domain Email Deliverability

Last updated on Jul 24, 2025

Troubleshooting Email Spam Rejection: How to Improve Domain Email Deliverability

Description:
A comprehensive guide designed for Brixly shared hosting customers to identify and resolve issues that cause emails to be marked as spam or rejected. This article details SPF record setup, essential email authentication methods, best practices, and practical troubleshooting steps using tools such as cPanel and Mail Tester.

Table of Contents

Understanding Email Spam Filtering

Modern email providers use advanced spam filtering to protect users from unwanted messages. If your emails are ending up in spam folders or being outright rejected, typical causes include:

  • Missing or misconfigured authentication records (SPF, DKIM, DMARC)
  • Blacklisted server or domain IP addresses
  • Problematic sending habits or email content
  • Attachments, links, or formatting that trigger spam filters

By understanding these causes, you can take targeted action to improve your email deliverability.

How Brixly Relays Outbound Email

All outbound emails from domains hosted on Brixly’s shared platform are processed through our secure email infrastructure. This setup ensures that:

  • Emails are dispatched using both your domain’s settings and our mail servers
  • Our systems enforce robust anti-spam measures
  • Proper authentication is used to maximize deliverability

> Tip:
> If you experience issues with email delivery, always begin by checking your domain’s SPF records.

SPF Records: What They Are and How to Set Them Up

SPF (Sender Policy Framework) is a DNS record that helps stop spammers from sending emails that appear to be from your domain. Without an accurate SPF record, your emails are more likely to be rejected or land in spam folders.

The Correct SPF Record for Brixly

To authorize Brixly’s mail servers, add this SPF record to your domain’s DNS:

v=spf1 a mx ip4:your_server_ip include:spf.hostns.io -all
  • Where to add:
    In cPanel, go to Zone Editor > select your domain > Manage > Add Record (or edit the existing SPF TXT record).

Step-by-Step: Adding an SPF Record in cPanel

  1. Log in to your cPanel account.
  2. Navigate to Zone Editor.
  3. Click Manage next to the domain you want to update.
  4. Search for the existing SPF record or click Add Record > Add TXT Record.
  5. Enter the following:
    • Name: yourdomain.com. (replace with your actual domain)
    • Type: TXT
    • TTL: 14400
    • Record: 
      v=spf1 a mx ip4:your_server_ip include:spf.hostns.io -all
  6. Save your changes.

> Note:
> If you use additional email services (e.g., Microsoft 365, Google Workspace), you must include their SPF mechanisms as well. For example: > > > v=spf1 a mx ip4:your_server_ip include:spf.hostns.io include:_spf.google.com -all >

Other Authentication Methods: DKIM & DMARC

DKIM (DomainKeys Identified Mail) and DMARC (Domain-based Message Authentication, Reporting & Conformance) provide additional layers of email authentication.

DKIM

  • Purpose: Ensures emails are not tampered with during transit by adding a digital signature.
  • How to Enable:
    In cPanel, use the Email Deliverability section. Locate your domain and click Manage to enable and copy the required DKIM record into your DNS.

DMARC

  • Purpose: Allows domain owners to specify how unauthenticated emails should be handled (quarantine, reject, or monitor only).
  • How to Enable:
    Create a TXT record in your DNS:
    • Name: _dmarc.yourdomain.com.
    • Type: TXT
    • Value: 
      v=DMARC1; p=quarantine; rua=mailto:you@yourdomain.com
    Adjust the policy (p=) and reporting address as needed.

General Best Practices for Avoiding Spam Filtering

To maximize deliverability, follow these proven guidelines:

  • Authenticate all outgoing email with SPF, DKIM, and DMARC records.
  • Keep content clean: Avoid using spam-triggering language, excessive links, or suspicious attachments.
  • Use consistent formatting and avoid large images or attachments that can trip filters.
  • Send from reputable domains and maintain a healthy sending reputation.
  • Monitor blacklists: Regularly check if your domain or server IP is listed on major blacklists (e.g., MX Toolbox).
  • Never purchase mailing lists and always use opt-in email lists.
  • Personalize emails and include a clear unsubscribe option.

Using Mail-Tester.com for Diagnosis

Mail-Tester.com is a free online tool to check your email’s spam score and diagnose deliverability issues.

How to Use Mail Tester

  1. Go to Mail-Tester.com.
  2. Copy the temporary email address displayed.
  3. Send a test email from your domain to this address.
  4. Return to the Mail-Tester page and click “Then check your score.”
  5. Review your score and detailed report, which will highlight any SPF/DKIM/DMARC issues, blacklistings, or content-related problems.

Use the feedback to resolve any issues before sending emails to your real recipients.

Troubleshooting Common Issues

If you’re still having trouble with email deliverability, consider these steps:

  • SPF/DKIM/DMARC Errors: Double-check that all authentication records are properly configured and have propagated.
  • Blacklisted IP/Domain: Run your domain and server IP through blacklist checkers. If listed, follow the delisting instructions provided by the blacklist.
  • Content Issues: Use Mail Tester or similar tools to identify problematic words, formatting, or attachments.
  • Third-party Email Providers: If you’re routing email through services like Microsoft 365 or Google Workspace, ensure their records are included in your SPF entry.
  • SMTP Authentication: Always use SMTP authentication when sending email from email clients. Lack of authentication can result in rejections.
  • Recipient Filters: Sometimes, issues are on the recipient’s side. Ask them to whitelist your email address or domain.

When to Contact Support

If you have followed all the troubleshooting steps and your emails are still being marked as spam or not delivered, reach out to our support team. Please provide:

  • The sender and recipient email addresses
  • The email subject and approximate send time
  • Any error messages received (copy the full message)
  • The full email headers (if available)
  • Steps you have already taken to troubleshoot

Our team will investigate further and guide you to a resolution.

Need additional help?
If you’re still experiencing difficulties, please raise a support ticket with all the relevant details. Our team is here to help ensure your email deliverability is as reliable as possible.