CENTRL sends email through multiple service providers for both redundancy and maximum coverage. It is recommended that customers whitelist the domain @oncentrl.com for all emails. This will ensure that all emails are delivered.
CENTRL does not maintain a list of IP addresses that should be white-listed as these IP addresses change periodically. If a list of whitelisted IP addresses must be used, customer should automate the query of CENTRL's SPF record. CENTRL's SPF record maintain the most accurate list of CENTRL's email IP addresses.
McAfee email gateway
Symantec Brightmail Appliance