Apple Mail does not offer creation of email signatures from HTML. Only a rich-text editing box is provided, without the ability for more customization.
HTML Email Signature – Mail enhances these capabilities by allowing customized creation of email signatures from HTML. Simply add your HTML, and your signature is created! A button to preview the HTML is also available.
** READ BEFORE PURCHASING **
– Valid HTML must be provided. This is not a design utility. Issues with formatting and/or appearance of the final signature are directly tied to the HTML code.
– An installed version of Apple Mail (included by default in Mac OS X and macOS) is required for this application to function.
