User Guide

Using Kaspersky SMTP-Gateway application 45
Before you enable this option, make sure that there is enough space in
your server’s file system to accommodate the archive.
Do not forget to periodically purge this directory to remove old mes-
sages and compress necessary files (the purging frequency depends
on the mail traffic intensity within your network).
5.3. Protection from hacker attacks
and spam
To provide highest level of security to your mail system, we recommend that you
modify the Kaspersky SMTP-Gateway configuration file to extend the anti-virus
functionality of the application. To protect your server from hacker attacks or, for
example, to prevent spam being relayed through your server, configure the
following options:
• DenyUnresolvedConnect in the [smtpgw.access] section of the ap-
plication configuration file. This parameter defines the application re-
sponse to an attempt to start an SMTP session from a host if it cannot
be defined by the IP address. If the parameter is set to true (DenyUn-
resolvedConnect=true), the application will try to determine the
name of the host that requested the mail connection. If the host name
cannot be determined, the application will close the mail session.
• DenyUnresolvedMailfrom in the [smtpgw.access] section of the
configuration file. This parameter limits reception of messages from IP
addresses that are not explicitly specified in your DNS settings. If this
option is enabled (DenyUnresolvedMailfrom=true), the application
will try to determine the IP address of the MX-record of the domain
contained in the sender address. If the IP address cannot be deter-
mined, messages are not sent or received from this IP address.
• Rule in the [smtpgw.access] section of the configuration file. This pa-
rameter limits the routing of messages via the application from certain
IP addresses only to some authorized domains. The value of this pa-
rameter is critical for preventing using the application as an open mail
relay.
A detailed discussion of the syntax of these command is provided in the
description of the configuration file (see A.2, page 74)