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payload_too_large

The request was rejected on arrival because of its size, before any field was read. Nothing was sent and nothing was charged.

Status: 413

{
  "status": 413,
  "type": "payload_too_large",
  "message": "Request body is too large. Pre-upload large attachments with POST /attachments.",
  "request_id": "req_01J8K2P...",
  "doc_url": "https://docs.epostix.com/errors/payload_too_large"
}

Why you got this​

  • A file was inlined in the send request instead of being uploaded first.
  • A batch carries up to 100 emails, and each one adds its own HTML body, attachments and metadata to the same request.
  • The HTML body embeds images as data URIs rather than linking to them.
  • A generated document or report was pasted into the message body.

How to fix it​

Upload each file with POST /attachments first, then reference the returned attachment id in the send request. That keeps the request small no matter how large the file is. A pre-uploaded attachment stays usable for 24 hours, after which referencing it returns attachment_expired.

If the attachments themselves go over the 40MB total limit, pre-uploading will not help and you get attachment_too_large. Split the message or link to the file instead. For a batch, send fewer emails per request.

Is it safe to retry​

No, not unchanged. Rebuild the request with attachment ids and send it again. Nothing was stored, so reusing the same Idempotency-Key is safe.