Updated 7 Nov 2026 · Checked against Client rendering rules · By Hilsio team
Short answer
ChatGPT email signatures usually break because the HTML uses things email clients ignore: CSS classes, flexbox, SVG icons and embedded base64 images. Paste the code into Hilsio's free fixer. It flags problems, rebuilds with tables and inline styles, re-hosts images and shows previews for Outlook, Gmail and mobile.
Checked 7 Nov 2026
Paste your ChatGPT signature
Fixed rules, not AI.
600 px · 3.4 kB · images hosted
Paste HTML and click Fix my signature to see what email clients will reject.
Join the generator waitlistAI tools output web-style HTML: flex layouts, class names, SVG icons, and base64 images. Outlook's Word renderer and Gmail's sanitizer strip most of that, so columns collapse and logos vanish.
Google Drive image links and chat attachment URLs often fail on send. Heavy markup can exceed Gmail's 10,000-character limit.
Paste your HTML. Hilsio runs deterministic rules: detect unsupported CSS, flag SVG and base64, estimate Gmail size, and recommend table-based rebuild with hosted https images. Full conversion ships in the generator; this page shows diagnosis before you copy.
After copy, paste into Gmail web settings, new Outlook › Settings › Accounts › Signatures, or classic Outlook File › Options › Mail › Signatures. iPhone Mail has limited HTML support—prefer Gmail or Outlook apps for logos.
Yes, ChatGPT can write signature HTML, but the code often uses CSS classes, flexbox, SVG icons or base64 images that Outlook and Gmail strip or block. Use ChatGPT for wording and layout ideas, then run the HTML through a fixer that rebuilds it with tables and inline styles before installing.
Classic Outlook for Windows renders email with a Word-based engine that ignores much modern CSS, including flexbox, grid and many margin and padding rules on divs. Rebuilding the layout as HTML tables with inline styles fixes most of these issues.
No. Hilsio's fixer applies fixed conversion rules: the same HTML in gives the same signature out. It does not redesign your signature or invent content. It lists changes so you can check the result before copying.
Gmail's signature box does not accept raw HTML directly. Open the HTML in a browser or tool preview, copy the rendered signature, then paste into Settings › General › Signature. If Gmail says it's too long, shrink images and inline code.
Related
Free signatures include one small “Created with Hilsio” text link.