I’ve spent some more time looking into this. Prefect’s MattermostWebhook should also expose ‘secure’ and pass that to apprise. Apprise does not work in its current form with secure=True and port=443 That combination is needed for our Mattermost. I am having to patch the Prefect code. And also apprise’s NotifyMattermost url method to remove line 328’s or self.port == default_port Can someone help me fix these things in the public repos? Or show me a way to get this to work with secure and 443?