The E-mail Attachment Filtering section configures the file extensions that are filtered by the SonicWALL.
Enable Rapid E-Mail Attachment Filtering - Select this feature to automatically block the most prevalent e-mail viruses on the current Rapid E-mail Attachment Block List.
Enable E-Mail Attachment Filtering of Forbidden File Extensions - Select this check box to filter E-mail attachments.
Forbidden File Extensions - Type the file extensions to be filtered in the Add Extension field. Hackers commonly spread viruses through Visual Basic and Windows Executable files, therefore "vbs" and "exe" are provided as default extensions for this feature. To add a file extension to the list, type the file extension in the Add Extension field and click Update. To delete a file extension, select the file extension from the list, and click Delete Extension.
In this section, the administrator chooses the action that the SonicWALL performs when filtering E-mail attachments. The attached file can either be deleted or it can be disabled by altering the file extension. In either case, the original E-mail text is still sent to the intended recipient.
Disable forbidden file by altering the file extension and attach warning text - Select this option to disable forbidden attachment files as they pass through the SonicWALL. The SonicWALL replaces the third character of file extensions with "_". If the E-mail attachment is a valid file, the E-mail recipient may return the attachment to its original file extension without damaging the file.
Delete forbidden file and attach warning text - Select this option to delete forbidden attachment files as they pass through the SonicWALL.
This is a warning message that can be customized and added to E-mails filtered by the E-mail Filtering Service. You can use the default message text or type in your own warning message in the Warning Message Text field up to 256 alphanumeric characters.
When you have configured the E-mail Filter settings, click Update. Once the SonicWALL has been updated, a message confirming the update is displayed at the bottom of the browser window.
Select Block SMTP E-Mail Fragments (Content-Type: message\partial) to enable blocking of partial e-mail messages. E-mail fragments are e-mail messages with the MIME Content-Type: message/partial in the header. Partial e-mails can be a security threat by allowing viruses to escape undetected by virus scanners because they are fragmented. The virus becomes fully functional once reassembled on the client.
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