HTML Email Signature

An HTML email signature is one constructed using HTML markup and inline CSS rather than plain text. HTML enables formatted typography, logos, photos, social media icons, banner images, clickable CTAs, and brand-aligned colors and layouts. The HTML used in email signatures is constrained: most email clients render with subsets of HTML and CSS that are decades behind modern web standards. Outlook desktop versions use Microsoft Word's rendering engine, which does not support flexbox, grid, or modern CSS layouts. Gmail strips embedded `<style>` blocks. Apple Mail and iOS Mail apply automatic link detection that can break formatted phone numbers and addresses. Production-quality HTML email signatures use table-based layout, inline CSS only, absolute pixel widths, MSO-conditional comments for Outlook fixes, and image dimensions chosen to survive automatic scaling. Most professional signature platforms generate HTML signatures from templates rather than expecting users to write HTML themselves.