Start (or upgrade to) the paid managed plan — returns a hosted Stripe Checkout link.

Subscribes the account to the single managed plan: $49 a month covers the first 3 mailboxes and each extra mailbox is $5 a month (3-mailbox / $49 minimum; no setup fee, no domain fee; an account already paying keeps its own minimum and price). mailboxes (3 or more) seeds the initial quote only — the billed quantity then TRACKS the account's live set-up mailbox count, never a commitment for mailboxes not yet set up. Returns a hosted Stripe Checkout URL to open and pay. mode is "simulated" only in a fully-unarmed test environment where no real purchase is possible; "stripe" once real billing is armed.