Configuring SMTP Message Rules

To set limits on the email messages that InterScan™ Messaging Security Appliance (IMSA) can handle and to control email relay, configure all settings on the messages rules screen.

Email Relay

To prevent spammers from using the IMSA MTA as a relay for spam, configure relay control. You will add the mail domains on your network to the Relay Domains list. When IMSA receives an email message, it looks at the final destination of the email and compares it to this list. IMSA discards the message under the following circumstances:

Relay domain settings are different from Domain-based delivery settings. For an explanation, see About Domain-Based Delivery.

To configure message rules:

  1. Choose Administration > IMSA Configuration > SMTP Routing from the menu. The SMTP tab displays by default.  

  2. Click Message Rule.

  3. Under Message Limits, configure the following:

 

The SMTP Message Limits precede any message limits specified in the scanning conditions of a policy rule. If the SMTP message limits are exceeded, Postfix will not transfer the messages to the scanners for policy matching.

 

  1. Under Relay control, select any of the following:

  2. Reject unknown sender domains.

  3. Reject unknown recipients. (by checking LDAP)—If you enable this option and IMSA cannot connect to the LDAP server, it will reject all email.

  4. Reject unknown IP address. (Enabling this option might impact IMSA performance.)

  1. Under Relay Domains, configure the following to ensure that Postfix relays messages only to internal domains:

    1. Under Add Domain, type the name of an email domain on your network; for example, mydomain.com.

    2. To add the domain to the list, click >>. To remove a domain, click it in the list, and then click <<.

    3. Import from file—Click to import relay domains from a file. The following shows sample content of a domain list text file:

IMSAtest.com

zzyy.aaabbbccc.org

dddeeefff.net

  1. Under Permitted Senders of Relayed Mail, select the host or specific IP addresses from which Postfix will accept and relay outgoing mails:

  192.168.1.1

 192.168.2.0:255.255.255.0

 192.168.3.1:255.255.255.128

 192.168.4.100

 192.168.5.32:255.255.255.192

1. The hosts specified under the Permitted Senders of Relayed Mail are not restricted to the internal domains specified under Relay Domains. In other words, you can add external IP addresses to the permitted senders list, such as those belonging to a branch office.
2. The imported text file may contain only one domain name per line.

 

  1. Click Save.

 

See also: