The current list of available monitor location IP's can be found in the link below and additional IP's we utilize for QA Regression Test.
Available Monitoring Locations:
QA Regression Test Servers:
AlertSite updates this page daily based on the information it has in its database. So, this page contains the most actual information.
Note that the firewalls running on the side of your checked website, email server or another resource should allow connections from these IP addresses.