Symantec Security 5600 Series, Security 5400 Series,Clientless VPN 4400 Series, Administration Manual

Page: 229 / 861

229 Defining your security environment
Controlling full application inspection of traffic
The most common way to protect your network is to force all email retrieval requests to pass through
the security gateway, as shown in
Figure 6-3 , instead of letting your employees connect directly to the
external server.
Figure 6-3 Inbound (POP3) mail example
EC-1 still sets the POP3 server settings in its email client software to be the DNS-resolvable name or IP
address of ES-2, but the traffic request first passes through the security gateway, where the source IP
address is changed to be that of the security gateway’s external interface. ES-2 thinks that the request
originated from the security gateway, so that is where it sends the reply. The security gateway
examines the email for any problems, changes the destination address to the real recipient (EC-1) and
forwards the email.
Configuring access for inbound and outbound email
Configuring access for SMTP and POP3 traffic lets users send and receive Internet email. Prior to
configuring access, you should determine what level of access is to be granted, and who should have
that access. You should also consider for whom you will relay email, what email you will accept, and if
you will send all email to the antivirus scan engine before it is allowed through the security gateway.
Prerequisites
None.
Manage electronic mail
To manage electronic mail, you must do the following:
■
Ensure the SMTP or POP3 proxy is enabled
■
Create an email service group
■
Create an allow rule for email
To ensure that the SMTP or POP3 proxy is enabled
1 In the SGMI, in the left pane, under Assets, click Proxies .
2
For SMTP traffic:
■
In the right pane, in the Proxies table, click SMTP , and then click Properties .
■
In the Proxy Properties dialog box, on the General tab, to enable the SMTP proxy, check
Enable .
■
In the Caption text box, type a brief description of the SMTP proxy.
■
Optionally, on the Description tab, type a more detailed description than you typed in the
Caption text box.
■
Click OK .
ES-1
ES-2
EC-1 EC-2
192.168.10.150
192.168.10.10
192.168.10.5 10.172.15.5 10.172.15.1 172.16.10.1
172.16.10.15
172.16.10.153