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.
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.
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:
About the SMTP-Proxy