Email expiration?

["Thiago Lima @ WF" <thiagolima () webforce com br>]

        Hi,

        There's any way to 'auto-destroy' na email sent after N days? 

        I'd like to send an email to someone and after N days the email
became unreadeble. Is that possible? I thougth about a certificate that
expires. Will that work? Does something like that exists?

Thanks alot.
Thiago Lima.