Create a broadcast draft

Create a draft for one list: from on a verified domain, subject, optional preview_text, and content as html and/or text, markdown, a block document in content, or a published hosted template ({id or key, optional version_id}). Markdown and block content are rendered with the workspace design (newsletter settings). Raw content supports merge tags such as {{first_name}}, {{fields.plan}}, and fallbacks like {{first_name | there}}; HTML values are escaped. audience narrows who gets it: segment_id (only list members matching a segment), limit (at most this many people), and order (signup, or engaged for most engaged first). tracking turns open and click tracking on or off (both on by default). web.enabled publishes the issue on the list's newsletter site once it is sent. To send later, create the draft, then call POST /broadcasts/{id}/schedule; scheduled_at is not accepted here.