pclan.us

Spam filters are set up on the Server which subscribes to a public list of known threats, spammers, and IP addresses with poor reputation known as blacklists.  Anyone's email address can potentially end up on a black list if that email address is used (either unknowingly or knowingly by the address owner) to send mass emails or is reported by the spam-reporting function that is built into the spam filters of all of the popular Anti Virus programs.  For example, when you right click an email in your Outlook Express email box and click Spam, Report as Spam or  a similar function --that is part of the Anti-Virus programs.

Lowering the SCL setting on the server from the default of 7 to a 5 significantly appeares to help block spam.

When we come across an email address that the Server is rejecting then we simply add it to the Exclusion or Bypass list in which emails from that address are not checked against the black lists or the SCL Thresholds.

These tactics listed here are widely accepted and used in IT to overcome obstacles relating to Spammers and Spam threats.

Configure Content Filtering Properties

http://technet.microsoft.com/en-us/library/bb124490.aspx

How to Specify Recipient and Sender Exceptions for Content Filtering

http://technet.microsoft.com/en-us/library/aa995952%28EXCHG.80%29.aspx