HTML Email Checker
HTML email presents unique deliverability challenges. Spam filters evaluate the structure of your HTML as closely as they evaluate your authentication records. An HTML email checker identifies code patterns that trigger filters — script tags, excessive image-to-text ratios, missing alt attributes, and high link density.
Email clients strip JavaScript from HTML emails, but including script tags still damages your spam score because filters treat them as a red flag. Similarly, emails that are almost entirely images with minimal text are flagged because spam campaigns frequently use this technique to evade content-based filters. Our checker calculates your HTML-to-text ratio and alerts you when it exceeds safe thresholds.
Try our free HTML Email Checker tool by pasting your HTML source directly in the browser. For comprehensive analysis including Gmail and Outlook scores, upload a full .eml file through your free account.
HTML patterns that hurt deliverability
- <script> tags — always stripped and always penalised
- HTML-to-text ratio above 60% signals image-spam tactics
- 1×1 tracking pixels that privacy-focused clients block
- Images missing alt text — accessibility and filter signal
- More than 10 external links triggers link-density filters