Limits, quotas, and suppression

Limits protect the platform and keep sending predictable. Some limits are technical, while others come from the Delivery account plan and configuration.

No Delivery account, no Send API quota

The Send API always runs through an existing Delivery account. The account defines the token, sending domains, quotas, and suppression-list settings used by /v1/send and /v1/send/bulk.

Send API technical limits

Limit	Value
`/v1/send` batch size	Up to `500` messages per request
`/v1/send/bulk` recipients	Up to `500` recipients per request
HTTP payload size	Up to `50mb`
Send request rate	`10` requests per second per Send API token

If you exceed the request rate, the Send API returns 429 and may include Retry-After.

Delivery account quotas

A Send API token belongs to a Delivery account. That account controls sending limits such as plan capacity, period limits, overdelivery behavior, account status, and assigned domains.

When a send request arrives, the API reserves quota before it queues messages. If quota is not available, the request is rejected before messages are accepted.

Common quota-related errors use 429, for example daily, monthly, yearly, or overquota limits.

Suppression list behavior

The suppression list prevents sending to recipients that should not receive email, such as addresses with previous bounces or complaints.

For Send API requests:

The API performs a suppression pre-check.
The pre-check estimates how many recipients should reserve quota.
The response includes suppression_summary.
Final suppression checks happen later during delivery.

Suppression summary is a pre-check

suppression_summary describes the API check before messages are queued. It is useful for visibility and quota estimates, but it is not the final delivery result.

Suppression summary statuses

Status	Meaning
`checked`	The pre-check completed successfully.
`ignored`	Suppression was ignored because of account or request configuration.
`unavailable`	The pre-check could not be completed; the API proceeds conservatively.
`not_applicable`	There were no recipients to check. This is unusual for valid send requests.

Example:

{
  "suppression_summary": {
    "status": "checked",
    "checked_recipients": 2,
    "accepted_recipients": 1,
    "suppressed_recipients": 1,
    "suppressed_emails": ["jane@example.com"]
  }
}

Manage suppression lists

Use the Management API to:

list suppression-list entries;
add an email address;
update reason, account scope, or active status;
delete an entry;
import or export suppression-list data.

Use the Send API response and Delivery TraceMail to understand how suppression affected a specific send.