Checks are performed every five minutes. When the below criteria are met an e-mail is sent by default. Recipients can be configured through the "Manage project security" part on home.mendix.com. Threshold cant be configured manually.
Application status: The internal state of your Mendix App is monitored in several ways. See the monitoring documentation page for a table with all the specific checks: https://world.mendix.com/display/howto40/Linux_Monitoring+using+Nagios
CPU check: This will cause a warning if your app exceeds 90% (No e-mail is sent) CPU usage and critical when it is at 100%.
Application/Database Server Up: Ping for network connectivity on the app node / database node.
Webserver: Whether your application is reachable over HTTP(s), the same way normal clients would connect to the app via their browser.
If you want a third party monitoring tool to integrate with our platform you can integrate it through these e-mails.