Email HTML Stripped by Email Clients
You designed beautiful HTML emails for your Replit app, but when recipients open them, the formatting is completely wrong. Images are missing, layouts are broken, CSS styles are stripped, and in some cases the email appears as plain text with raw HTML tags visible.
Email clients (Gmail, Outlook, Apple Mail, Yahoo) are notoriously aggressive about stripping HTML and CSS that they consider unsafe. Unlike web browsers, email clients do not support modern CSS, JavaScript, or many standard HTML features. Each client strips different things in different ways.
AI-generated email templates almost always use modern web CSS (flexbox, grid, external stylesheets, CSS variables) that email clients will strip or ignore entirely, leaving your carefully designed emails looking broken.
Error Messages You Might See
Common Causes
- External CSS stylesheets — email clients strip <link> tags and only support inline styles
- Modern CSS features — flexbox, grid, CSS variables, and media queries are not supported by most email clients
- JavaScript in emails — all JavaScript is stripped by every email client
- Background images via CSS — many clients ignore CSS background-image properties
- Unsupported HTML tags — email clients strip <div> positioning in favor of table-based layouts
- Image hosting issues — images linked from localhost or Replit dev URLs are not accessible from email clients
How to Fix It
- Use inline CSS only — put all styles in style="" attributes directly on HTML elements, never in <style> tags or external files
- Use table-based layouts — email HTML requires <table> elements for layout, not div/flexbox/grid
- Use an email framework — libraries like MJML, React Email, or Maizzle generate email-safe HTML from modern syntax
- Host images externally — use Cloudinary, S3, or your CDN for email images with absolute HTTPS URLs
- Test across clients — use Litmus or Email on Acid to preview your emails in Gmail, Outlook, Apple Mail, and Yahoo
- Include a plain text fallback — always send a multipart email with both HTML and plain text versions
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Get HelpFrequently Asked Questions
Why does my email look fine in Gmail but broken in Outlook?
Outlook uses Microsoft Word's rendering engine for HTML emails, which has extremely limited CSS support. You must use table-based layouts and inline styles for Outlook compatibility.
Can I use CSS flexbox in emails?
No. Flexbox, grid, and most modern CSS features are not supported by major email clients. Use HTML tables for layout and inline styles for formatting.
What is the easiest way to create email-safe HTML?
Use MJML (mjml.io) — it lets you write simple markup that compiles to email-safe HTML with table layouts and inline styles automatically.