Attachments

SIZE_BYTES="$(wc -c < invoice.pdf | tr -d ' ')"
ATTACHMENT_ID="$(
  curl -sS -X POST "https://smtp.sendmux.ai/api/v1/emails/attachments?filename=invoice.pdf" \
    --header @- \
    -H "Content-Type: application/pdf" \
    -H "Content-Length: $SIZE_BYTES" \
    --data-binary @invoice.pdf <<< "Authorization: Bearer $SENDMUX_API_KEY" \
  | jq -r '.data.attachment_id'
)"

{
  "from": { "email": "hello@example.com" },
  "to": { "email": "user@example.com" },
  "subject": "Invoice attached",
  "html_body": "<p>Please find your invoice attached.</p>",
  "attachments": [{ "attachment_id": "att_tz4a98xxat96iws9zmbrgj3a" }]
}

SIZE_BYTES="$(wc -c < invoice.pdf | tr -d ' ')"
SHA256="$(shasum -a 256 invoice.pdf | awk '{print $1}')"

UPLOAD_INTENT="$({
  curl -sS -X POST https://smtp.sendmux.ai/api/v1/emails/attachment-uploads \
    --header @- \
    -H "Content-Type: application/json" \
    -d "{
      \"filename\": \"invoice.pdf\",
      \"content_type\": \"application/pdf\",
      \"size_bytes\": $SIZE_BYTES,
      \"sha256\": \"$SHA256\"
    }" <<< "Authorization: Bearer $SENDMUX_API_KEY"
})"

ATTACHMENT_ID="$(
  printf '%s' "$UPLOAD_INTENT" \
  | jq -r '
      .data as $upload
      | "request = \($upload.method | @json)",
        "url = \($upload.upload_url | @json)",
        ($upload.headers | to_entries[] | "header = \("\(.key): \(.value)" | @json)")
    ' \
  | curl -sS --config - --data-binary @invoice.pdf \
  | jq -r '.data.attachment_id'
)"

{
  "from": { "email": "hello@example.com" },
  "to": { "email": "user@example.com" },
  "subject": "Invoice attached",
  "html_body": "<p>Please find your invoice attached.</p>",
  "attachments": [
    {
      "filename": "invoice-2026-03.pdf",
      "content": "JVBERi0xLjQKMSAwIG9iago8PAovVHlwZSAvQ2F0YWxvZw...",
      "type": "application/pdf"
    }
  ]
}