Understanding Spam Filters
Modern spam filters use machine learning to analyze hundreds of factors. Here’s how to stay in the inbox:
Technical Setup
1. Email Authentication
- SPF (Sender Policy Framework)
- DKIM (DomainKeys Identified Mail)
- DMARC (Domain-based Message Authentication)
- BIMI (Brand Indicators for Message Identification)
2. Infrastructure
- Dedicated IP address for large volumes
- Proper reverse DNS setup
- Regular IP warming for new domains
Content Optimization
1. Text-to-Image Ratio
- Keep images under 20% of email
- Always include alt text
- Don’t use image-only emails
2. Link Management
- Avoid URL shorteners
- Use your own domain for tracking
- Limit links to 2-3 per email
3. HTML vs Plain Text
- Use simple, clean HTML
- Include plain text version
- Test in multiple clients
Sending Best Practices
1. Volume Control
- Start with 50-100 emails per day
- Increase by 20% daily
- Never exceed domain reputation limits
2. Timing Optimization
- Tuesday-Thursday, 10 AM – 2 PM
- Avoid weekends and holidays
- Test time zones for international lists
Monitoring Tools
- GlockApps (Spam testing)
- Mail-Tester.com (Free analysis)
- Sender Score (Reputation monitoring)