First, you'll need to set up a new incoming webhook in your team's Mattermost configuration. An incoming webhook is a method for Mattermost to receive incoming messages to be posted to your Mattermost team from external services.
Now you can add your Mattermost's webhook to the integrations' section:
integrations: mattermost: - url: url1 - url: url2
You can also go further and connect other popular Polyaxon integrations to Mattermost using Zapier.