Custom tracking hostnames.tracking_options now accepts an optional domain_name so link and open tracking on message sends, scheduled sends, drafts, and Transactional Send can use your own verified tracking domain instead of the Nylas default.
Contact metadata.Contact requests and responses now support the metadata object and metadata_pair filtering, matching the metadata support already available on Events, Messages, and Drafts.
messages.send_raw_mime() sends a raw RFC 822 MIME message through POST /v3/grants/{grant_id}/messages/send?type=mime, using the new SendRawMimeRequest model.