Preventing a Symantec SMTP product from being used as an open relay server

Article:TECH81304  |  Created: 2003-01-11  |  Updated: 2004-01-22  |  Article URL http://www.symantec.com/docs/TECH81304
Article Type
Technical Solution

Environment

Issue



This page describes how to prevent external users form using your Symantec SMTP product server as an open SMTP relay.


Solution



It is important that your Symantec SMTP product server is configured to accept mail only for your local email domain.

To protect your server, do the following procedures in the order given.


Relay configuration
To set up the Local Routing List to have mail relayed correctly
  1. Do one of the following to open the Administration page for the Symantec SMTP product.
    • In Symantec Mail Security for SMTP 4.0, click Start > Programs > Symantec Mail Security for SMTP.
    • In Symantec AntiVirus for SMTP Gateways 3.0, click Start > Programs > Symantec AntiVirus for SMTP Gateways 3.0 > Symantec AntiVirus for SMTP Gateways 3.0.
  2. Type in the user name and password created during the installation of the Symantec SMTP product and then click Logon.
    • In Symantec Mail Security for SMTP 4.0, click Blocking Policy.
    • In Symantec AntiVirus for SMTP Gateways 3.0, click Configuration.
  3. Click Routing tab.
  4. Under Local Routing List, click Add.
  5. In the Host or Domain field under "Routed host or domain," type your email domain.

    Your email domain is everything that appears after the @ symbol in your email address. For example, if your email address is administrator@Brightcorp.com, your domain is Brightcorp.com.
  6. In the Host or Domain field under Destination Relay (Optional), type the IP address of your mail server.
  7. In the Port field, ensure that the number matches the port that the mail server is using. The default is port 25.
  8. Click Save.
  9. If you have multiple domains, click Add, and then repeat steps 6 through 9.


Preventing Unauthorized Relays

To prevent external users from relaying mail, do the following from the Symantec SMTP product administration dialog box
  1. Do one of the following in the Symantec Product Administration interface:
    • In Symantec Mail Security for SMTP 4.0, click Filtering Policy.
    • In Symantec AntiVirus for SMTP Gateways 3.0, click Blocking Policy.
  2. Click Anti-Relay.
  3. Click Do Not Allow, Except for listed hosts.
  4. In the space provided, type the IP address of your internal mail server or servers to allow mail to be relayed correctly, as shown below.


  5. Click Save Changes.


Preventing unauthorized relays based on special characters in email address (optional)
Relaying can be prevented by rejecting emails that contain special characters in the email address. Do the following from the AV for SMTP administration dialog box.

To configure to reject special characters
  1. Do one of the following in the Symantec Product Administration interface:
    • In Symantec Mail Security for SMTP 4.0, click Filtering Policy.
    • In Symantec AntiVirus for SMTP Gateways 3.0, click Blocking Policy.
  2. Click Anti-Relay.
  3. Check Reject messages with email addresses that contain any of the following characters (no spaces or commas between entries).
  4. In the box provided, type the following:
    %!&

    The following is an example of the Anti-Relay tab.

  5. Click Save Changes.







Legacy ID



2003061111362854


Article URL http://www.symantec.com/docs/TECH81304


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