What makes HTML email-safe
Email clients strip style sheets, scripts and most modern layout CSS. SignaturesDB uses nested tables with role="presentation", inline styles, absolute https image URLs with explicit width, height and alt text, and tel: and mailto: links, which is the format Gmail, Outlook and Apple Mail handle best.
Images are never embedded as base64 or blob: data, which many clients block. If an image isn't hosted yet, the editor tells you before you export.
Where to paste HTML
Thunderbird and many CRM, helpdesk and signature-management tools have an HTML field. Use Copy HTML for those. For Gmail, Outlook and Apple Mail, use Copy signature instead, which pastes the rendered result.
Frequently asked questions
Can I edit the HTML after exporting?
Yes. The code is plain, formatted HTML. Keep the table structure and inline styles if you make changes so it still renders in email.
Does the HTML include CSS classes or a <style> block?
No. All styling is inline because many email clients remove <style> blocks and ignore classes.