Before an email from an unknown sender reaches the inbox, outlook could
automatically reply to the return address of the message with a "code" and
instructions that the sender must use the code in the subject line before the
email message will be accepted.
This is a one time action and the email address would be automatically
accepted in the future.
The code should be displayed in non machine readable format to prevent
automatic mailing programs processing the code.
June 12th 2006

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