Email marketing has undergone a significant transformation in 2025. With new bulk sender requirements from Gmail and Yahoo, along with advanced filtering through Google's RETVec technology, marketers are rediscovering an old-school approach: plain text emails. This guide examines the data to help you make informed decisions about your email format strategy.
Key Email Format Research Findings
60%
Customer conversions from plain text
49%
Non-customer conversions from plain text
62%
Marketers using hybrid approach
23-37%
Lower opens with images vs plain text
The 2025 Inbox Landscape: What's Changed
Email filtering has evolved significantly. Gmail and Yahoo now enforce strict bulk-sender requirements, and Google's RETVec system uses machine learning to detect patterns that indicate spam.
The RETVec Effect
RETVec (Resilient & Efficient Text Vectorizer) is Google's new spam detection system that:
- Analyzes text patterns using vectorization
- Detects manipulative formatting tricks
- Rewards emails that mirror human-to-human communication
- Penalizes overly designed emails with hidden text or image-only layouts
The 0.3% Complaint Rate Threshold
Current compliance requirements include:
- Complaints above 0.3% can result in delivery issues
- One-click unsubscribe is mandatory
- Authentication (SPF, DKIM, DMARC) is required
- List hygiene and permission are critical factors
Plain Text Vs HTML: The Performance Data
Open Rate Comparisons
Research consistently shows simpler formats outperform complex HTML:
| Format | Open Rate | Notes |
|---|---|---|
| Plain Text | Highest | Consistent across multiple studies |
| Simpler HTML | Medium | Outperforms HTML-rich designs |
| Complex HTML | Lowest | Triggers spam filters more often |
A software platform that switched from templated HTML to plain-text notes saw open rates jump to approximately 60%, largely by escaping Promotions-style filtering.
Conversion Performance
Analysis of over 1,000 campaigns reveals significant conversion differences:
- Plain text with existing customers: 60% of conversions
- Plain text with non-customers: 49% of conversions
- HTML emails: Lower conversion rates for both segments
Click-Through Rate Data
Controlled tests show that adding images or GIFs to identical copy produced 23-37% lower open rates compared to plain-text versions. When copy reads like a one-to-one note with short, specific content and one link, click-to-open rates improve because there are fewer competing elements.
For teams implementing cold email campaigns, our guide on how to write cold emails that get responses covers format selection as part of a comprehensive outreach strategy.
Specific use cases where plain text emails consistently outperform HTML designs
Personalized Outreach
Mimics human communication for higher perceived authenticity, ideal for B2B sales outreach and cold email campaigns.
Transactional Emails
Order confirmations, shipping notifications, password resets, and account alerts work best in simple formats.
Urgent Communications
Crisis communications, deadline reminders, and time-sensitive offers benefit from clear, direct messaging.
Building Trust
First impressions matter--plain text excels for new subscriber welcome sequences and re-engagement campaigns.
Scenarios where HTML design adds genuine value to email marketing
Visual Merchandising
E-commerce product showcases, fashion brands, and visual-heavy promotional campaigns need HTML presentation.
Brand Reinforcement
BIMI displays verified logos in the inbox and can produce 10% average open-rate lifts with proper authentication.
Promotional Campaigns
Catalog-style emails with multiple offers benefit from structured layouts, clear CTAs, and product galleries.
Newsletter Layouts
Mixed content including multiple articles, section headers, and sponsored content needs organized HTML structure.
The Hybrid Approach: Best of Both Worlds
Research shows 62% of marketers now use hybrid approaches--selecting format based on purpose and audience.
Strategic Format Selection
Match format to purpose:
- Use plain text for direct outreach and relationship building
- Use HTML for visual promotions and newsletters
- Test audience preferences regularly
Different email types serve different purposes. Our comprehensive overview of 6 types of emails every marketer should consider provides guidance on matching format to each email category.
Minimal HTML Best Practices
When using HTML, keep it clean:
- Inline critical CSS for consistent rendering
- Use text-to-image ratios (aim for 60/40 text to image)
- Avoid JavaScript and complex animations
- Test across email clients and devices
- Include plain-text alternatives
Testing and Optimization
Continuous improvement matters:
- A/B test formats by segment
- Monitor deliverability metrics
- Track engagement by email type
- Adjust based on audience response
For teams looking to automate these decisions, our AI & Automation services can help build intelligent email workflows that select the optimal format automatically.
| Aspect | Plain Text | HTML Email |
|---|---|---|
| Open Rates | Highest | Medium to Low |
| Development Time | Minimal | Moderate to High |
| Design Flexibility | None | High |
| Spam Filter Risk | Low | Higher |
| Mobile Readability | Excellent | Varies |
| Personalization | Natural | Template-based |
| Best For | Outreach, Transactions | Promotions, Newsletters |
Frequently Asked Questions
Do plain text emails really get better open rates?
Yes, multiple studies confirm that plain text emails consistently achieve higher open rates than HTML emails. This is partly because they avoid spam filter triggers and partly because they feel more personal and authentic to recipients.
Should I switch all my emails to plain text?
Not necessarily. The research supports a hybrid approach where you match the format to the purpose. Use plain text for personalized outreach, transactions, and relationship-building. Use HTML for visual promotions, product showcases, and complex newsletters.
How does RETVec affect email deliverability?
Google's RETVec uses machine learning to analyze text patterns and detect spam. It rewards emails that look like normal human correspondence and penalizes overly designed emails with manipulative formatting, hidden text, or image-heavy layouts.
What is the ideal text-to-image ratio for HTML emails?
Aim for approximately 60% text to 40% images. Too many images without sufficient text can trigger spam filters and cause display issues when images are blocked.
Does HTML email still have a place in 2025?
Absolutely. HTML email remains valuable for visual merchandising, brand reinforcement with BIMI, promotional campaigns with multiple offers, and complex newsletters. The key is using HTML appropriately--not over-designing and ensuring text content dominates.
Conclusion
The data is clear: in 2025, email success increasingly depends on choosing the right format for your purpose. Plain text emails consistently outperform HTML in open rates and conversions for many use cases, particularly personalized outreach and transactional communications. However, HTML remains valuable for visual merchandising and brand reinforcement.
The key insight is that most successful marketers now use a hybrid approach--selecting format based on purpose, audience, and goals. This data-driven approach to email format, combined with proper authentication and list hygiene, positions marketers for success in the evolving inbox landscape.
Rather than asking "plain text or HTML?", smart marketers ask "which format serves this specific communication goal best?" The answer depends on your audience, your purpose, and your willingness to test and optimize over time.
Ready to optimize your email marketing strategy? Our AI & Automation services can help you implement data-driven email approaches that improve engagement and conversions. We also offer email marketing services for comprehensive campaign management.
Sources
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Geeks for Growth - Plain-Text Wins the Inbox - Gmail/Yahoo 2025 rules, RETVec filter, complaint rate thresholds, open rate data
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HubSpot - Plain Text vs HTML Emails Data - Simpler HTML vs HTML-rich performance, plain-text best performer
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IInfotanks - HTML Vs Text Emails Insights - 1000+ campaign data, 60% customer conversion, 49% non-customer conversion
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Databox - HTML vs Plain Text Marketers Survey - 62% of marketers use hybrid approach