Watermark and User Notification

[Donnie D. Quindardo]

- Configure MailScanner to notify users that their attachments have been 
  blocked.

- Configure MailScanner to use Watermarks and note that messages that 
have no sender and no watermark are spam.

- Send an e-mail through MailScanner with an attachment that is banned, 
perhaps "test.com".

- Look in the spam quarantine of MailScanner, the notification e-mail 
that is sent to the user is there. That's because it is sent with an 
envelope address of <> and does not get a MailScanner Signature beforehand.