Sending mail through script fails. It is throwing the following error in the logs:
Dec 2 11:30:15 user py_limit_out: ERROR Rejecting forged message: PPP_SENDER_VHOST_ID is present in environment, but its value is empty Dec 2 11:30:15 user plesk sendmail: handlers_stderr: DATA REPLY:554:5.7.0 Your message could not be sent. The sender's domain is not registered in Panel, or is misconfigured.#012REJECT
Mail settings misconfiguration.
Allow scripts and users to use Sendmailoption is enabled in Home > Tools & Settings > Server-Wide Mail Settings
Rebuild mail server configuration using Plesk self repair utility:
# plesk repair mail