Debugging Email Delivery and Spam/Junk Folder Issues Print

Emails landing in the spam or junk folder can harm communication and brand trust. This guide provides a structured approach to diagnosing and fixing deliverability problems, drawing on best practices and insights from Mailtrap’s recommendations.

1. Confirm the Problem

• Send test emails to different providers (Gmail, Outlook, Yahoo, corporate domains).
• Check full message headers for SPF, DKIM, and DMARC results.
• Identify if the issue is domain-wide, IP-specific, or campaign-specific.
• Note if problems started after changes (new IP, DNS updates, template changes).

2. Authentication Checks

SPF

• Ensure your domain has a valid SPF record authorizing sending servers.
• Example: v=spf1 include:_spf.google.com ip4:203.0.113.25 -all

DKIM

• Configure DKIM to sign outgoing emails with your domain’s private key.
• Verify headers show DKIM-Signature and pass alignment.

DMARC

• Publish a DMARC policy to instruct receivers how to handle failing emails.
• Example: v=DMARC1; p=none; rua=mailto:dmarc-reports@yourdomain.com; adkim=s; aspf=s

3. Sender Identity & Compliance

• Use a consistent and recognizable “From” name and address.
• Include a monitored Reply-To address.
• Always display a physical mailing address and unsubscribe link.

4. List Hygiene

• Use explicit opt-in, preferably double opt-in.
• Remove hard bounces and inactive subscribers regularly.
• Never use purchased lists.
• Enable feedback loops to suppress complainers.

5. Content Optimization

• Avoid spammy subject lines (e.g., “FREE!!!” or “Act Now”).
• Keep body text professional; avoid excessive caps or exclamation marks.
• Use HTTPS links and avoid URL shorteners.
• Limit or avoid risky attachments.

6. HTML Best Practices

• Use clean, responsive HTML with inline CSS.
• Optimize images and add alt text.
• Maintain a healthy text-to-image ratio.
• Include a plain-text version of your email.

7. Engagement Signals

• Segment audiences and personalize content.
• Run re-engagement campaigns for inactive users.
• Use A/B testing to refine subject lines and CTAs.

8. Reputation & Blocklists

• Check if your domain/IP is listed on blocklists.
• Warm up new IPs gradually with engaged recipients.
• Maintain consistent sending patterns.

9. Legal & Platform Requirements

• Provide one-click unsubscribe options.
• Comply with GDPR, CAN-SPAM, and other regional laws.
• Keep privacy policies updated and transparent.

10. Infrastructure Checks

• Ensure reverse DNS/PTR records resolve correctly.
• Use valid HELO/EHLO hostnames.
• Support TLS for secure delivery.

11. Testing & Monitoring

• Use tools like Mailtrap to test spam scores and rendering.
• Monitor analytics for open rates, clicks, and complaints.
• Iterate continuously based on feedback.

Quick Troubleshooting Flow

1. Collect samples and headers.
2. Verify SPF, DKIM, DMARC alignment.
3. Check sender identity and compliance.
4. Review content for spam triggers.
5. Audit HTML and include plain-text version.
6. Clean lists and suppress bounces.
7. Check blocklists and reputation.
8. Retest with engaged segments.

References

This article is based on industry best practices and insights from Mailtrap’s guide on email spam issues.