Buttondown: posting rules and settings

What a Buttondown channel accepts in Postemi: media, limits, required fields, and the fields of the settings object for the API.

Basics

Rules

• You connect with the API key of your newsletter (Buttondown: Settings > API). It works on every Buttondown plan.
• With status "send" the e-mail goes to your subscribers at the scheduled time; Postemi confirms Buttondown's first-send check for it. With "draft" it is saved in Buttondown and not sent.
• The subject is the subject setting, or else the first line of the text.
• Beta: not yet tested with many newsletters.

Settings fields

These fields go into the post's settings object, alongside the __type field. In the UI, you fill in the same ones in the channel's settings section.

Examples

Each example is one item in the POST /public/v1/posts request's posts array. The envelope around it is always this:

{
  "type": "schedule",
  "date": "2026-09-15T09:00:00.000Z",
  "shortLink": false,
  "posts": [ /* the item below */ ]
}

{
  "integration": { "id": "<channel-id>" },
  "value": [{ "content": "<p>The text of the post.</p>", "image": [] }],
  "settings": { "__type": "buttondown" }
}

The channel ID comes from the channel list, and the path values for images and videos from media upload. The exact schema for the connected account comes from the settings schema endpoint. From the command line, the same thing is the --settings flag. See the CLI examples.