SMTP-Proxy: Content Types

Certain kinds of content embedded in email can be a security threat to your network. Other kinds of content can decrease the productivity of your users. You can use the ruleset for the SMTP-Incoming proxy action to set values for incoming SMTP content filtering. You can use the ruleset for the SMTP-Outgoing proxy action to set values for outgoing SMTP content filtering. The SMTP-proxy allows these content types: text/*, image/*, multipart/*, and message/*. You can add, delete, or modify rules.

You can also configure the SMTP-proxy to automatically examine the content of email messages to determine the content type. If you do not enable this option, the SMTP-proxy uses the value stated in the email header, which clients sometimes set incorrectly. For example, an attached .pdf file might have a content type stated as application/octet-stream. If you enable content type auto detection, the SMTP-proxy recognizes the .pdf file and uses the actual content type, application/pdf. If the proxy does not recognize the content type after it examines the content, it uses the value stated in the email header, as it would if content type auto detection were not enabled. Because hackers often try to disguise executable files as other content types, we recommend that you enable content type auto detection to make your installation more secure.

Configure Rules

  1. On the Edit page for the proxy, select the Proxy Action tab.
  2. From the Attachments drop-down list, select Content Type Rules.
    The Content Type Rules page appears.

Screen shot of the SMTP-Incoming Edit Proxy Action page, Content Types category, Rules tab

  1. To enable the SMTP-proxy to examine content to determine content type, select the Enable content type auto detection check box.
  2. Configure the rule action.
    For more information, see Add, Change, or Delete Rules.
  3. To change settings for another category in this proxy, see the topic for that category.
  4. Click Save.

If you modified a predefined proxy action, when you save the changes you are prompted to clone (copy) your settings to a new action.

For more information on predefined proxy actions, see About Proxy Actions.

Configure Body Encryption Settings

Your XTM device detects the body encryption settings in an email based on PGP MIME types. To specify the encryption requirements for the body content of the email messages that are sent through your network, you can configure the settings for Body Encryption. You can add rules to allow or deny an email message based on the encryption criteria you specify. When you configure the rules for encrypted content, you can specify the actions to take for messages from a particular email address to a particular email address, or you can use wildcards to add global rules that apply to all email messages. Rules are applied to email messages in the order you specify in the Encrypted Content Rules list. Make sure to arrange the rules in your list in the best order for your organization.

From the Content Types page:

  1. From the Attachments drop-down list, select Body Encryption.
    The Body Encryption settings appear.

Screen shot of the Content Types Body Encryption page

  1. To add a new rule, click Add.
    The Add Rule dialog box appears.

Screen shot of the Add Rule dialog box

  1. In the To Address text box, type a valid email address.
    To use a wildcard, type *@*.
  2. To set a specific From Address, in the From Address text box, type an email address.
  3. To set the action the proxy takes for this rule, from the Action drop-down list, select an option:
  4. Click OK.
    The rule appears in the Body Encryption list.
  5. To change the order of the rules in the list, select a rule and click Move Up or Move Down.
  6. To disable a rule in the list, clear the Enabled check box.

See Also

About the SMTP-Proxy

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