GET /v1/mail/free-tier
What a free mailbox is, and what it costs to provide.
Authentication
Send an API key as a bearer token. The key must carry the mail.view permission; a key without it is refused with 403, not 404.
This endpoint takes no organisation id. Your key already identifies the organisation it belongs to, and the response is scoped to it.
Try it
Replace anything in angle brackets with your own values, and the key placeholder with a key from your dashboard.
curl -X GET https://api.zinndigital.com/v1/mail/free-tier \
-H "Authorization: Bearer zdk_live_…"Signed in? The API console in your dashboard fills in your real organisation id and your own key, and runs the request against the live API so you can see the actual response. Open this endpoint in the API console
Details
The free mailbox tier's quota, per-organization ceiling and derived capacity. Requires mail.view. ⭐ Published rather than written down. Every figure is computed from the measured relay capacity and the configured quota, so raising the quota lowers the mailbox count and raises the stated per-mailbox cost with no second edit. A screen or a pricing page that restated these numbers would be a second expression of the same arithmetic, and would go stale the first time the quota moved.
Response
| Name | Type | Required | What it is |
|---|---|---|---|
available | boolean | Yes | Whether free mailboxes are actually on offer. Two measured legs, not a switch. The first is "does mail land on our own relay" — true exactly when every mail hostname we… |
unavailable_cause | string<relay, headroom, > | Yes | Which leg refused, so that two situations sharing one symptom stay distinguishable. relay means the mail hostnames are not ours — a routing decision. headroom means the relay… |
reserve_percent | integer | Yes | How much of the relay is held back from the free tier for the mail somebody is paying for. Free and paid mailboxes share one disk, and the failure this prevents is a paying… |
offerable_bytes | integer | Yes | Usable storage less the reserve — what the free tier may draw on. |
committed_bytes | integer | Yes | Storage already promised to mailboxes on the relay — every mailbox, not only free ones, because a paid mailbox occupies the same disk. |
headroom_bytes | integer | Yes | Offerable storage still unpromised. Negative when the relay is oversubscribed. |
unavailable_reason | string | Yes | Why free mailboxes are not on offer, in a sentence an operator can act on. Empty when available is true. Names our own configuration rather than any supplier. |
relay_zone | string | Yes | The apex of our own mail relay — the name available compares against. |
quota_mb | integer | Yes | Per-mailbox size of a free mailbox, in MB. |
per_org_ceiling | integer | Yes | How many free mailboxes one organization may hold. A ceiling rather than a target, and the only term a customer can move — which is what stops the offer running away. |
usable_bytes | integer | Yes | Mail-available storage on one relay node, measured rather than assumed. |
node_monthly_eur | integer | Yes | What one relay node costs per month. |
mailboxes_per_node | integer | Yes | How many fully-used free mailboxes one node holds. |
orgs_per_node | integer | Yes | How many organizations one node holds if every one fills its ceiling. |
worst_case_cost_per_mailbox_eur | number | Yes | What a free mailbox costs per month, fully used. Worst case deliberately: a figure computed from average fill is a claim about customer behaviour dressed as a cost, and it is… |
Errors this endpoint can return
401 · 403 · 429