how to fight fake email addresss?

[Jason]

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Hi,

    I'm running an email server to serve only our own employee. So I would
like to make some special treatment for emails coming to or going out from
users of our server. The treatment I want to make includes spam checking,
email splitting, and attachment filename checking.

    I know rules are designed to do the job. But will MailScanner fight
against fake email addresses? If not, people can fake our email address and
get thru.

Jason

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