Cancel the subscription, at the end of the billing period (default) or immediately.

HTTP-only (not an MCP tool). The body is optional; an empty body means { "immediate": false }. Default (immediate: false): the account is marked canceling as soon as this call lands, campaigns already running keep sending until the paid period ends (see sendingStopsAt on GET /account), then all sending stops (an account that is not paid up stops sending at once), and mailboxes and domains are NOT released by this call (teardown is null). immediate: true: the account is marked canceled, campaigns are stopped, every mailbox is released right away and cannot be brought back, and domains we bought for you are released too (a connected domain is not touched); teardown counts what was released. Calling it again after an immediate cancel returns the recorded teardown with alreadyCanceled: true and releases nothing more. The dashboard Billing page calls this same route. The call tells Stripe before it changes the account: the default stops the subscription from renewing (periodEndsAt is the end of the paid period, from Stripe, when sending continues until then), and immediate: true ends the subscription at Stripe now with no proration, credit or refund. If Stripe refuses or gives no clear answer, nothing changes on the account and the call answers 502.