HTML signature
A formatted email signature built from HTML so it can include layout, links and images.
An HTML signature is a small fragment of web markup added to the end of an email. Unlike a plain-text signature, it can contain a photo, a logo, coloured text, clickable icons and buttons.
Email clients support a much older subset of HTML than browsers. Reliable signatures use nested tables for layout, inline styles instead of style sheets, web-safe fonts and images hosted at absolute HTTPS URLs.
Gmail rejects signatures longer than 10,000 characters of HTML, so compact markup matters.