Preventing the reverse NDR attackYou can use a combination of recipient filtering and tar pitting to protect your server against the reverse NDR attack.
Install the Intelligent Message Filter on all SBS installationsBecause the IMF is a free tool and does not conflict with other antispam tools, it should be installed on all SBS servers.
Route outbound email through a smart hostTo protect against current and future problems that could impact your server's capability to deliver mail to other servers reliably, you should configure your server to send all outbound email through your ISP's SMTP server.
Use the POP3 Connector as a transitional tool, not as a mail solutionIf you must use the POP3 Connector at all, use it only to transition mail services away from POP3 toward full SMTP.
Setting appropriate SCL values using OutlookEnable the display of SCL values in the Outlook client and monitor the operation of the IMF to determine the ideal values to set for Gateway Blocking and Junk E-mail Delivery configurations.
