Surf Control 5.2.4 Benutzerhandbuch

SurfControl RiskFilter - E-mail V5.2.4

Administrator’s Guide

5

A lower MX preference number gives higher priority than a lower one. In Figure 1-2, 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 
distribution and timely failover. Using load-balancing switches may improve the overall efficiency of your 
SMTP infrastructure.