Surf Control 5.2.4 Benutzerhandbuch

152 Administrator’s Guide

SurfControl RiskFilter - E-mail V5.2.4

A lower MX preference number gives higher priority than a lower one. In Figure 5-25, e-mail is sent in the 
following way:

• E-mail sent to site A.com round-robins between mail exchangers 1, 2,and 3, because each RiskFilter 

appliance has the same MX preference of 5. 

• The same thing happens for e-mail sent to site B.com. If site A is down (e.g., with a network failure), the 

sending mail server will route e-mail to the fourth (failover) MX record, which is the address of a server 
in a different physical location.

For the described failover to work properly, RiskFilter appliances at site A are configured to accept 
messages for site B, and RiskFilter appliances at site B are configured to accept messages for site A. 

The failover servers have static routes configured so that RiskFilter knows where to route the e-mail. There 
are also advanced load-balancing switches that can be used for these purposes. These switches offer a 
variety of load-balancing algorithms, in addition to round-robin delivery, which provide efficient load distri-
bution and timely failover. Using load-balancing switches may improve the overall efficiency of your SMTP 
infrastructure.

RiskFilter in a cluster set up. You can set up RiskFilter in a cluster and use the wizard to set the IPs of 
the master and slave/s:

 RiskFilter in a cluster set up

• Internet – E-mails coming into slave. Slaves can only be accessed via port 25 from the internet.

• Network 1 – Used for communication between master and slave.

• Network 2 – The network where the internal servers lie. This network holds mail servers and the 

RiskFilter administration clients.

To configure multiple NICs, see Multi-NIC configuration in RiskFilter on page 142.