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In Exchange 2003 we had many tools provided to help eliminate spam. Some are Intelligent Message Filtering, Connection Filtering, and Sender ID. As you can see below they are all configurable in the ESM on the Message Delivery Properties.
In Exchange 2007 these tools are still there as well as new ones like Anti-Spam Stamps. These are viewable in Outlook 2007 by looking at the message options. The lien X-MS-Exchange-Organization-Antispam-Report is the line that you want.
Attachment filtering is something new in Exchange 2007. This is one of the few things that can not be managed via the Exchange Management Console (EMC) and can only be done via the Exchange Management Shell (EMS). It is enabled by default on servers that have the Edge role installed. You can determine this by using the Get-TransportAgent cmdlet.
In order to see the current settings you would use Get-AttachmentFilterEntry. You would use the Type and Name fields if you wanted to make a change to those as we will see later.
To add a new attachment filter that filters e-mail attachments that have a specific MIME content type, use the following command:
Add-AttachmentFilterEntry -Name <MIMEContentType> -Type ContentType
In the example below we are filtering all JPEG images.
In the next example we are filtering all files by File name (using type FILENAME) and blocking all files that have the extension “.mov”.
And in the 3rd example we are blocking a particular file by name. In this case a file named “virus.ppt”.
To remove the filters, we use Remove-AttachmentFilterEntry and the type:name. Here we are getting rid of the filter for “virus.ppt”.
Now what we do when we match the filter is called the action. Below we used Get-AttachmentFilterListConfig to see the settings. Our action here is to Reject the message and issue an NDR to the user with a reject message: “Message rejected due to unacceptable attachments.”
You could set an action to strip the attachment or to silently delete it.
Using the Set-AttachmentFilterListConfig command we are setting the action to strip the attachment.
Next: Part 5 – More Anti-Spam Configuration in 2007