Email preheader preview builder

The hidden div goes straight after the opening body tag of the email template, before any visible content. Its padding is a run of zero-width characters long enough to fill the snippet, so nothing from the body follows the preheader into the inbox. Width fits here come from a per-character estimate at a 14 px snippet font, not a real client render: Gmail, Outlook and Apple Mail each measure and cut differently, so treat the previews as close approximations.