SpamTitan Cloud is comprised of three different server clusters, one of which you will be using. The easiest way to determine which cluster you are using is to examine the MX records for your domain. You can check your MX record using MXToolBox.
Your MX records will contain either:
The IP address ranges for the different clusters are:
cloud1.spamtitan.com & cloud2.spamtitan.com
cloud3.spamtitan.com & cloud4.spamtitan.com
cloud6.spamtitan.com & cloud6.spamtitan.com