Why Your Emails Go to Spam and How to Fix It

Your emails hit spam due to missing authentication, poor sender reputation, spammy content, or engagement issues. Fix authentication first, then warm up your domain and optimize content.

Your product sends password resets, signup confirmations, and feature announcements. But users aren’t getting them because they’re stuck in spam folders. Here’s exactly how to fix it.

The 5 Critical Issues Killing Your Email Delivery

1. Missing Email Authentication (Fix This First)

Problem: Email providers can’t verify your emails are legitimate without proper authentication records.

Solution: Set up these DNS records immediately:

SPF Record:

v=spf1 include:_spf.google.com include:mailgun.org ~all

SPF verifies that your emails have been sent from your domain.

DKIM Record: Your ESP (SendGrid, Mailgun, etc.) provides this CNAME record. Add it to your DNS. DKIM guarantees that your emails are not changed after they are sent.

DMARC Record:

v=DMARC1; p=none; rua=mailto:dmarc@yourdomain.com

DMARC helps protect your domain from attacks, phishing emails, etc. Start with p=none to monitor, then move to p=quarantine.

Custom Tracking Domain: Set up a custom tracking domain to track open and click rates in your emails safely.

2. Poor Sender Reputation & Domain Warmup

Problem: New domains or those with bad sending history get automatically filtered.

The Email Warmup Process: Email warm-up gradually increases the number of emails sent from your account to boost your email engagement and deliverability.

Manual Warmup Steps:

Week 1: Send 10-20 emails daily to engaged users
Week 2: Increase to 50-100 emails daily
Week 3: Scale to 200-500 emails daily
Continue gradually building your domain reputation with ESPs

Quick Fixes:

Use a dedicated subdomain for transactional emails (mail.yourapp.com)
Monitor bounce rates (keep under 2%)
Track spam complaints (keep under 0.1%)
Use dedicated IP addresses to control your email reputation

3. Content and Spam Trigger Issues

Problem: Your emails contain spam trigger words or suspicious formatting patterns.

Top 12 Spam Words to Avoid: Free, Guarantee, Urgent, Limited time, Act now, Click here, Special offer, Buy now, Deal, Winner, Congratulations, Cash

Content Best Practices:

Use clear and honest language that focuses on the value you’re providing
Maintain a 60% text to 40% images ratio
Avoid ALL CAPS and excessive exclamation marks!!!
Ensure that the promise in your subject line matches the content of your email
Use simple variables to personalize your emails instead of complex HTML

Technical Content Rules:

No link shorteners (use full URLs or hyperlinked text)
Avoid attachments – they’re known to carry viruses
Clean, simple HTML coding
Include alt text for all images

4. List Quality and Management

Problem: Sending to invalid addresses, spam traps, or unengaged users hurts your reputation.

List Building Best Practices:

Build a lead list from scratch using organic methods rather than purchasing lists
Verify your email list to prevent bounces and invalid addresses
Avoid spam traps – email addresses set up to catch bad senders

List Maintenance:

Remove hard bounces immediately
Use tools like Debounce or Bouncer to verify email list quality
Clean inactive subscribers regularly
Always include an unsubscribe button to prevent spam complaints

5. Low Engagement and Monitoring

Problem: Poor engagement rates signal to ESPs that your content isn’t welcome.

Engagement Optimization:

Personalize your emails to prevent them from looking like spam
Segment your audience and tailor content based on their interests and behavior
Ask recipients to reply to your emails to show active engagement

Monitoring Methods:

Use seed lists – test email addresses across different providers to monitor inbox placement
Track open rates, click rates, and bounce rates
Monitor spam complaint rates using tools

Provider-Specific Guidelines

Gmail Optimization

Gmail uses advanced machine learning and AI to analyze every email.

Gmail Best Practices:

Warm up your emails by starting with smaller volumes to engaged users
Ask recipients to add you to their contact list
Simplify your HTML and limit URLs – aim for 60:40 text-to-HTML ratio
Stay clear of blacklists by regularly monitoring your domain status

Microsoft Outlook/Hotmail

Outlook’s Junk Email Filter uses heuristic analysis, user feedback, and Bayesian filtering.

Outlook Best Practices:

Use a trusted email domain and manage sender reputation
Use clear, honest subject lines avoiding sensational language
Clean your email list regularly by removing inactive users

Technical Implementation Checklist

DNS Configuration

# Check your current records
dig TXT yourdomain.com
dig TXT _dmarc.yourdomain.com

Required Records:

[ ] SPF record with your ESP’s include statement
[ ] DKIM CNAME record from your ESP
[ ] DMARC policy (start with p=none)
[ ] MX Record to help providers know what servers accept emails for your domain
[ ] Custom tracking domain setup

Email Infrastructure

[ ] Use business domain (not Gmail/Yahoo for sending)
[ ] Set up dedicated sending subdomain
[ ] Configure proper Reply-To addresses
[ ] Implement bounce handling
[ ] Always include an unsubscribe button in every email

Code-Level Implementation

For Transactional Emails:

// Example: Proper email headers
const mailOptions = {
  from: '"YourApp" <noreply@mail.yourapp.com>',
  replyTo: 'support@yourapp.com',
  to: user.email,
  subject: 'Password Reset - YourApp',
  html: emailTemplate,
  headers: {
    'List-Unsubscribe': '<mailto:unsubscribe@yourapp.com>'
  }
};

Testing and Monitoring Tools

Spam Testing

Use spam checker tools to analyze your email content and get a deliverability score
Test using seed lists across different email providers
Mail-Tester.com for spam score analysis

Deliverability Monitoring

Monitor your deliverability score before, during, and after sending campaigns
Google Postmaster Tools (Gmail insights)
Microsoft SNDS (Outlook data)
Your ESP’s analytics dashboard

Email Authentication Verification

Use technical setup checkers to verify your SPF, DKIM, and DMARC configuration
MXToolbox for DNS record verification
DMARC Analyzer for policy monitoring

Sending Best Practices

Natural Sending Patterns

Send emails correctly by keeping a natural pace that matches human behavior.

Sending Guidelines:

Don’t send all emails at once
Spread your campaigns throughout the day
Avoid sending during weekends or holidays for business emails
Maintain consistent sending schedules

Personalization at Scale

Use custom tags to personalize emails efficiently:

Company name
Industry
Recent activity/behavior
Role or department

Quick Implementation Guide

Week 1: Foundation

Set up SPF, DKIM, DMARC records
Configure custom tracking domain
Audit current email templates
Remove obvious spam trigger words

Week 2: Optimization

Start domain warmup process
Implement proper email headers
Set up monitoring tools
Clean email lists

Week 3: Testing

Run emails through spam checkers before sending
Test deliverability across providers
Monitor engagement metrics
Adjust based on results

Ongoing: Maintenance

Monitor deliverability scores regularly
Clean inactive subscribers monthly
Update DNS records as needed
Track and improve engagement rates

Emergency Troubleshooting

If emails suddenly stop delivering:

Verify DNS records – Check if SPF, DKIM, DMARC are still active
Review spam complaints – Check for unusual complaint spikes
Test across providers – Send test emails to Gmail, Outlook, Yahoo
Check blacklist status – Use monitoring tools to verify domain reputation
Contact your ESP – They can provide delivery attempt logs

The Technical Reality

Only one thing can stop your emails from going to the spam folder: your deliverability. Email authentication isn’t optional—it’s infrastructure. Missing these records is like running HTTP instead of HTTPS in 2025.

Priority Order: