New endpoints added for managing custom SMTP connections: GET/POST /v2/smtp/connections for listing and creating connections, GET/PUT/DELETE /v2/smtp/connections/{connectionId} for reading, updating, and removing a single connection, and POST /v2/smtp/connections/{connectionId}/test for verifying that a connection works
New endpoints added for managing the sender addresses used with those connections: GET/POST /v2/smtp/senders for listing and adding senders, and DELETE /v2/smtp/senders/{email} for removing one