ZyXEL Communications ZYWALL USG 2000 Support Notes page 173

ZyWALL USG 2000 Support Notes
websites.
The following figure shows that ZyWALL succeed to identify the spam mail by using DNSBL
function and tag the suspected spam emails. There are many DNSBL websites can be referred,
for example, zen.spamhaus.org, dul.dnsbl.sorb.net, list.dsbl.org and combined.njabl.org
3.3.2.1.2 Scenario II: Company's Email server located in the DMZ
The other scenario presents that email server is located inside the intranet. It means that the
email server behind the ZyWALL. In this scenario, the better way to filter spam mails is to
scan them when outside email want to establish the connection with our email server. In other
words, scan all incoming emails before they are received by our email server. Hence, we must
scan based on the SMTP protocol and DNSBL.
173
All contents copyright (c) 2008 ZyXEL Communications Corporation.