Overview
Email deliverability isn’t just about avoiding spam folders—it’s about creating emails that email providers recognize as legitimate, valuable communication. This guide covers best practices backed by real case studies.Dark Mode Optimization
Critical for modern email success
Quality HTML Signals
Professional structure beats plain-text
Engagement Metrics
Better design = better inbox placement
Dark Mode Optimization
Why It Matters
Over 60% of email users prefer dark mode. Emails that break in dark mode signal poor quality to email providers, negatively affecting deliverability.Case Study Finding: Emails with proper dark mode support show significantly higher inbox placement rates and better consistency across email clients.→ Read Full Case Study
Best Practices Checklist
Test both modes - Always preview in light and dark mode before sending
Maintain contrast - Ensure text remains readable in both modes
Preserve branding - Colors should look professional in dark mode, not washed out
Test CTAs - Buttons must be visible and clickable in both modes
Consider images - Some logos/graphics may need dark mode variants
How Migma Handles Dark Mode
Migma automatically optimizes emails for dark mode across all major clients:- Automatic color adaptation - Smart color inversion that preserves brand identity
- Cross-client testing - Works across Gmail, Outlook, Apple Mail, Yahoo
- Text contrast - Ensures readability without manual CSS media queries
- Layout preservation - No broken layouts or invisible elements
Testing Dark Mode
Using Email Preflight:1
Open Email in Editor
Navigate to your email conversation
2
Run Preflight
Click ”📋 Preflight” button
3
Select Dark Mode Devices
Choose devices with dark mode support:
- Gmail (Dark)
- Apple Mail (Dark)
- Outlook (Dark)
4
Review Screenshots
Check for:
- Text readability
- Color contrast
- Button visibility
- Brand consistency
5
Fix Issues
Use conversational prompts: “Fix dark mode text contrast”
Common Dark Mode Issues
White text on white background
White text on white background
Problem: Text becomes invisible in dark modeSolution:
- Ensure background colors are explicit, not transparent
- Use Migma’s automatic dark mode optimization
- Test with Email Preflight before sending
Logo disappears in dark mode
Logo disappears in dark mode
Problem: Dark logo on dark background becomes invisibleSolution:
- Upload a light version of your logo for dark mode
- Add subtle border or background to logo area
- Use SVG logos that adapt to background
Brand colors wash out
Brand colors wash out
Problem: Colors look unprofessional in dark modeSolution:
- Test your brand colors in dark mode during brand setup
- Adjust brightness/saturation for dark mode variants
- Migma handles this automatically for most brands
Quality HTML vs Plain-Text
The Plain-Text Myth
Many believe plain-text emails perform better for deliverability, especially in cold outreach. Research shows the opposite is true.Why Plain-Text Fails
Low Effort = Spam Signals:- Plain-text mass emails are trivial to generate
- Spam filters associate plain-text with low-effort spam
- No engagement metrics (time spent, scroll depth, clicks)
- Most spam uses plain-text to avoid HTML filtering
- Cold outreach tools mass-send plain-text
- Legitimate businesses use professional HTML
- Users spend less time with plain-text emails
- Minimal visual hierarchy = harder to scan
- No interactive elements (buttons, links, images)
- Email providers track engagement and reward quality
Why Quality HTML Wins
Professional Signals:- Well-structured HTML = legitimate business communication
- Clean code demonstrates technical competence
- Proper email standards (semantic HTML, accessibility)
- Users spend more time with well-designed emails
- Visual hierarchy improves readability and scanning
- CTAs generate measurable click behavior
- Higher engagement = positive signals to email providers
- Email providers evolved beyond “plain-text = human, HTML = spam”
- Machine learning recognizes quality vs mass spam
- Professional HTML is expected from businesses
Best Practices for HTML Quality
Use semantic HTML - Proper structure with tables for layout
Optimize images - Compress images, use proper alt text
Clean code - No bloated CSS, inline styles, minimal attributes
Responsive design - Mobile-friendly layouts that adapt
Email standards - CAN-SPAM compliance, unsubscribe links
Test rendering - Verify across email clients with Preflight
How Migma Ensures Quality
Migma generates production-ready HTML that follows best practices:- React Email Framework - Industry-standard email components
- Clean Code Generation - No bloat, optimized output
- Cross-client Compatibility - Works across 40+ email clients
- Accessibility - Semantic HTML, proper ARIA labels, alt text
- Responsive by Default - Mobile-first design approach
- Standards Compliance - CAN-SPAM, GDPR, email best practices
Engagement Optimization
Time-on-Email Metrics
Email providers track how long recipients spend reading your emails. Higher engagement = better inbox placement. Best Practices:Visual Hierarchy - Use headers, sections, white space for scannability
Compelling Content - Hook readers in first 2-3 seconds
Readable Typography - 14-16px minimum, proper line height
Strategic CTAs - Clear, prominent calls-to-action
Mobile Optimization - 60%+ of emails opened on mobile
Click-Through Signals
Clicks demonstrate value and engagement to email providers. Best Practices:Clear CTAs - Primary action obvious and compelling
Button Design - Minimum 44px touch targets for mobile
Link Relevance - Every link should provide value
Link Text - Descriptive anchor text (not “click here”)
Test Links - Use Preflight to validate all links work
Reply Rates
Replies are the strongest positive signal for email providers. Best Practices:Personal From Address - Use real person, not noreply@
Conversational Tone - Invite dialogue when appropriate
Questions - End with question when relevant
Reply Path - Ensure Reply-To is monitored
Image Optimization
Image-to-Text Ratio
Too many images = spam signal. Aim for balanced content. Best Practices:60/40 Text Rule - Aim for 60% text, 40% images
Alt Text - Descriptive alt text for all images
Compression - Keep images under 100KB when possible
Format - Use JPG for photos, PNG for graphics
Fallbacks - Email works without images loading
Migma Image Optimization
- AI-Generated Images - Automatically optimized for email
- Smart Compression - Maintains quality while reducing size
- Alt Text Generation - AI-powered alt text for accessibility
- Responsive Images - Scale appropriately on mobile
Link Best Practices
Link Density
Too many links can trigger spam filters. Best Practices:Limit Links - 3-5 links maximum for promotional emails
Relevant Destinations - Every link should add value
HTTPS Only - Always use secure links
No Redirects - Avoid unnecessary redirect chains
Valid URLs - Test all links before sending
Unsubscribe Links
Required by law and good for deliverability. Best Practices:Always Include - Every promotional email needs unsubscribe link
One-Click - Make it easy (angry users mark as spam)
List-Unsubscribe Header - Include email header for one-click
Visible - Don’t hide in tiny footer text
Process Quickly - Remove within 24-48 hours
Link Validation
Use Email Preflight to automatically check:- Broken links (404 errors)
- HTTPS vs HTTP
- Redirect chains
- Malformed URLs
- Unsubscribe link presence
Spam Score Optimization
Common Spam Triggers
Avoid these patterns that raise spam scores:Target Spam Score
Aim for under 5/10 spam score Email Preflight automatically checks spam score and provides recommendations.How to Improve Spam Score
1
Run Email Preflight
Get your current spam score
2
Review Flagged Issues
See what’s triggering filters
3
Fix Issues
- Remove excessive punctuation
- Use sentence case
- Replace spam trigger words
- Add unsubscribe link
4
Re-test
Confirm score improved
Authentication & Infrastructure
Email Authentication
While Migma generates the email HTML, your sending infrastructure needs proper authentication. Required Setup:SPF Record - Authorize sending servers
DKIM Signature - Cryptographic email signing
DMARC Policy - Define authentication policy
Custom Domain - Send from your domain, not generic
Warm-up - Gradually increase sending volume
Sender Reputation
Your domain and IP reputation impact deliverability. Best Practices:Clean Lists - Remove bounces and inactive users
Low Complaint Rate - Under 0.1% spam complaints
Consistent Volume - Don’t spike sending suddenly
Monitor Metrics - Track bounce rate, complaints, opens
Use ESP Best Practices - Follow your ESP’s guidelines
Testing Before Sending
Email Preflight Checklist
Before sending any important campaign, run Email Preflight and verify:Device Rendering - Test on 30+ real devices
Dark Mode - Verify both light and dark modes
Link Validation - All links work correctly
Spam Score - Under 5/10
Grammar Check - No typos or errors
Mobile Responsive - Works perfectly on mobile
Accessibility - Alt text, contrast, semantic HTML
Send Test Emails
Before mass sending:Send to yourself - Review in your own inbox
Test different clients - Gmail, Outlook, Apple Mail
Check spam folder - Ensure it lands in inbox
Test on mobile - Open on actual mobile device
Click all links - Verify destinations
Monitoring & Improvement
Key Metrics to Track
Delivery Rate
Target: 98%+Percentage successfully delivered (not bounced)
Inbox Placement
Target: 90%+Percentage landing in inbox (not spam)
Open Rate
Target: 20-30%Industry average varies by sector
Click Rate
Target: 2-5%Percentage clicking links in email
Spam Complaint
Target: Under 0.1%Users marking as spam
Bounce Rate
Target: Under 2%Invalid or inactive addresses
Continuous Improvement
1
Establish Baseline
Track metrics for first 3-5 campaigns
2
A/B Test
Test subject lines, CTAs, layouts
3
Monitor Trends
Watch for declining performance
4
Clean Lists
Remove inactive subscribers quarterly
5
Update Content
Refresh stale email templates
6
Stay Updated
Follow email deliverability best practices
Quick Reference
Pre-Send Checklist
Copy this checklist for every campaign:- Email Preflight run and passed
- Dark mode tested on 3+ clients
- All links validated and working
- Spam score under 5/10
- No typos or grammar errors
- Mobile responsive verified
- Unsubscribe link present and working
- Images compressed and optimized
- Alt text on all images
- Subject line tested (not spammy)
- From address is personal (not noreply)
- Test email sent to team
- Reviewed in actual inbox (not preview)
Related Resources
Dark Mode Case Study
Research findings on dark mode and deliverability
HTML vs Plain-Text Study
Why quality HTML outperforms plain-text
Email Preflight
Test emails on 30+ real devices
FAQ: Deliverability
Common deliverability questions