Microsoft Exchange - reduce backscatter

These steps should be implemented to stop your Exchange Server getting blacklisted for "backscatter"

• Create a recipient filter to prevent Exchange Server from accepting messages that are sent to recipients who do not exist

• For Exchange 2003 this is described in step 2 here: http://support.microsoft.com/kb/909005 which also gives an early Microsoft summary of the problem
• For Exchange 2007 Hub servers and later you first need to enable the anti-spam functionality by running cd "c:\Program Files\Microsoft\Exchange Server\Scripts" and  /install-AntispamAgents.ps1 as described here http://technet.microsoft.com/en-us/library/bb201691%28v=exchg.80%29.aspx and then go to Edge Transport (or Hub Transport as appropriate) > Anti-spam tab > Recipient Filtering and enable it as described here http://technet.microsoft.com/en-us/library/bb125187%28v=exchg.80%29.aspx
• For Exchange 2010, instructions are similar to 2007, go to properties >  Blocked recipients and ensure "Block messages set to recipients that do not exist in the directory" is ticked as described  here and here
• For Exchange 2013, see here http://technet.microsoft.com/en-gb/library/bb201691%28v=exchg.150%29.aspx to enable Exchange anti-spam and then here http://technet.microsoft.com/en-gb/library/bb123891%28v=exchg.150%29.aspx and here http://technet.microsoft.com/en-us/library/bb125187.aspx to stop backscatter.  The EMC command is "Set-RecipientFilterConfig -Enabled $true" Set-RecipientFilterConfig -RecipientValidationEnabled:$true

• Stop the generation of non-delivery notifications (bounces) altogether as described here: http://support.microsoft.com/kb/294757

We have tested the above settings and have seen excellent results!