# Nylas Python SDK v6.15.0

Source: https://developer.nylas.com/docs/changelogs/2026-04-24-nylas-python-v6-15-0/

## Added

- **Transactional Send** — New `client.transactional_send.send(domain_name, request_body, …)` targets `POST /v3/domains/{domain_name}/messages/send`. Behavior aligns with grant `messages.send`: `from_` serializes to `from`, requests switch from JSON to multipart once attachments cross the 3 MB threshold, and stream attachments are base64-encoded for JSON sends. See the [Transactional Send quickstart](/docs/v3/getting-started/transactional-send/) and the [API reference](/docs/reference/api/transactional-send/send-transactional-email/).

- **Manage Domains API** — New `client.domains` resource for `/v3/admin/domains` with `list`, `create`, `find`, `update`, `destroy`, `get_info`, and `verify`. Use it to programmatically register and verify custom domains for Transactional Send and Agent Accounts. See the [Manage Domains guide](/docs/v3/email/domains/).

- **Nylas service account request signing** — New `ServiceAccountSigner` in `nylas.handler.service_account`, plus an optional `signer` argument on every `Domains` method. When a signer is provided the SDK attaches `X-Nylas-Kid`, `X-Nylas-Nonce`, `X-Nylas-Timestamp`, and `X-Nylas-Signature` headers, using canonical JSON so the signed bytes match what's sent on the wire. Adds `cryptography` as a dependency.

- **Policies API** — New `client.policies` resource exposes full CRUD against `/v3/policies` with typed models for query params, create/update bodies, and nested response data (`options`, `limits`, `spam_detection`). Policies are the container that governs which Rules and Lists apply to an [Agent Account](/docs/v3/agent-accounts/policies-rules-lists/).

- **Rules API** — New `client.rules` namespace covers the full Rules surface: `list`, `create`, `find`, `update`, `destroy`, and list rule evaluations. Works with the recently added [outbound rules](/docs/changelogs/2026-04-17-outbound-rules/) and recipient-based conditions. See the [Rules API reference](/docs/reference/api/rules/create-rule/).

- **Lists API** — New `client.lists` resource with full list CRUD and list-item operations: list, create, find, update, delete lists; list, add, and remove list items. Use a single managed allow-list or deny-list across both inbound and outbound Rules via the `in_list` operator.

## Fixed

- **`ListGrantsQueryParams` camelCase keys** — `sortBy`, `orderBy`, and `grantStatus` were being sent to the API as-is and silently ignored. They're now normalized to `sort_by`, `order_by`, and `grant_status` at serialization time. Type hints prefer snake_case going forward, and the camelCase fields are kept as deprecated aliases for backwards compatibility.