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Email drafts and A/B tests

The Email channel (newsletter in the API) writes email campaigns for your connected provider: Mailchimp, Brevo, HubSpot, Klaviyo, or beehiiv. Reactor never sends email. Publishing an email piece creates a ready-to-send draft in the provider; you review and send it there.

Email pieces in the editor​

Email pieces carry more than a body:

  • Subject and Preview fields above the content (preview text is the inbox snippet after the subject). The subject defaults from the piece title.
  • A Send via row: the provider connection, the list (beehiiv calls it a publication; HubSpot picks recipients inside HubSpot), and an optional template. Draft creation, scheduling, and the preview all default from this row.
  • Tabs: content (the body), a/b when the A/B toggle is on, and preview - the body merged server-side into the picked provider template, exactly what the draft will carry.

Reactor lists templates from Mailchimp, Brevo, and Klaviyo; HubSpot templates stay in HubSpot, and beehiiv posts use the publication's styling. Email always generates as a clean body first; the template is applied on the piece afterwards, from the Send via row.

A/B tests​

The A/B toggle next to the subject adds the a/b tab: version B's subject, preview text, and body, in its own editor. Both versions save and version together with the piece.

When the draft is created you set the test: the percentage of the list each version's test group gets (default 20), the test window in hours (default 4), and the winner by open or click rate. After the window, the winner goes to everyone else.

Mailchimp and Brevo take the A/B setup natively on draft creation. The provider-side test runs on subject and preview, so version B's body is finalized in the provider before sending. Klaviyo and HubSpot drafts are created normally and the test is configured inside the provider; beehiiv has no A/B over its API.

Creating the draft​

Publish ▾ → Draft in [provider] opens the draft dialog, preloaded with the piece's Send via and A/B setup. Confirm the list, subject, and test settings, and Reactor creates the draft campaign in the provider, with a deep link to open it there where the provider exposes one.

Scheduling a draft​

Email pieces schedule like any post: Publish ▾ → Schedule for later… with the email connection as the target. At the scheduled time Reactor creates the draft in the provider with the piece's list, template, and A/B setup, and notifies you. The hand-off never locks the piece the way a published post does - it is still just a draft until you send it.

Over MCP​

create_email_draft builds the draft headlessly; list_email_lists and list_email_templates enumerate the provider's lists and templates.