Email Troubleshooting

A practical guide to diagnosing and fixing common email issues.

Table of contents

1. Common Email Problems
   1. 1. Cannot Send Emails
   2. 2. Cannot Receive Emails
2. Authentication Issues
   1. 1. SPF Failures
   2. 2. DKIM Problems
   3. 3. DMARC Issues
3. Delivery Problems
   1. 1. Bounced Emails
   2. 2. Spam Filter Issues
4. Performance Issues
   1. 1. Slow Email Client
   2. 2. Synchronization Problems
5. Advanced Diagnostics
   1. Reading Email Headers
   2. Network Diagnostics
6. Best Practices
   1. 1. Preventive Measures
   2. 2. Security Practices
   3. 3. Maintenance Tasks
7. When to Seek Help
8. Additional Resources

Common Email Problems

❗ Before You Start

Always verify your internet connection is working before troubleshooting email-specific issues.

1. Cannot Send Emails

Symptoms:

• “Message failed to send” errors
• Emails stuck in outbox
• SMTP connection errors

Diagnostic Steps:

# Check SMTP server availability
ping smtp.gmail.com

# Verify DNS resolution
nslookup smtp.gmail.com

# Test email server ports
telnet smtp.gmail.com 587

Common Solutions:

• Verify SMTP server settings
• Check username/password
• Confirm port numbers (25, 587, 465)
• Update SSL/TLS settings

2. Cannot Receive Emails

Symptoms:

• Missing expected emails
• Delayed reception
• Incomplete synchronization

Diagnostic Steps:

# Check mail server records
nslookup -type=mx yourdomain.com

# Verify server response
telnet pop.gmail.com 995

Common Solutions:

• Check POP3/IMAP settings
• Verify storage space
• Clear local cache
• Update email client

Authentication Issues

Email authentication process and potential failure points

1. SPF Failures

Check SPF Records:

# View SPF record
nslookup -type=txt domain.com

Common Issues:

• Missing SPF record
• Incorrect server IP in record
• Syntax errors in SPF
• Too many DNS lookups

2. DKIM Problems

Verify DKIM:

• Check DKIM signature in headers
• Validate key rotation
• Confirm DNS records

💡 DKIM Tip

Most email clients can show you the DKIM signature status in the email headers.

3. DMARC Issues

Check DMARC Policy:

# View DMARC record
nslookup -type=txt _dmarc.domain.com

Troubleshooting Steps:

1. Verify DMARC record exists
2. Check policy syntax
3. Review alignment with SPF/DKIM
4. Monitor DMARC reports

Delivery Problems

1. Bounced Emails

Types of Bounces:

• Hard bounces (permanent)
• Soft bounces (temporary)
• Delayed delivery notices

Common Causes:

1. Invalid recipient address
2. Server rejection
3. Full mailbox
4. Policy violation

2. Spam Filter Issues

If Emails Go to Spam:

1. Check sender reputation
2. Review content for triggers
3. Verify authentication
4. Check IP blacklists

⚠️ Blacklists

Being on an email blacklist can severely impact delivery. Regularly check your IP against major blacklists.

Performance Issues

1. Slow Email Client

Optimization Steps:

1. Clear cache
2. Compact mailbox
3. Remove large attachments
4. Update client software

2. Synchronization Problems

IMAP Troubleshooting:

1. Check folder settings
2. Verify quota usage
3. Test connection speed
4. Reset sync state

Advanced Diagnostics

Reading Email Headers

Received: from mail-yw1-f41.google.com
    by mx.domain.com with ESMTPS
    id ABC123; Thu, 23 Feb 2024
Authentication-Results: spf=pass dkim=pass

Key Header Fields:

• Received lines (trace route)
• Authentication results
• Message ID
• Date stamps

Network Diagnostics

# Test email server connectivity
telnet smtp.gmail.com 587

# Check DNS resolution
dig +short mx gmail.com

# Verify reverse DNS
nslookup IP_ADDRESS

Best Practices

1. Preventive Measures

• Regular backup of emails
• Update client software
• Monitor storage usage
• Check authentication setup

2. Security Practices

• Enable 2FA
• Use strong passwords
• Keep software updated
• Monitor for unusual activity

3. Maintenance Tasks

• Clean inbox regularly
• Archive old emails
• Update contact lists
• Check spam folder

When to Seek Help

Contact your email provider or IT support when:

• Persistent authentication failures
• Systematic delivery problems
• Security compromises
• Complex configuration issues

📝 Documentation

Always document troubleshooting steps and results for future reference.

Additional Resources

• Email protocol documentation
• Server configuration guides
• Command Cheatsheet
• Authentication setup tutorials