Mime-mapping to trigger e-mail client

[Rob Hunt]

I've got RFC822 e-mail messages stored in a database.  I'd prefer *not* to 
write (or rely on) an email-to-HTML converter.  Instead, I'd like to serve the 
content as-is and have the client's browser recognize the mime type and trigger 
an e-mail client.  My question is, what mime-mapping will produce this behavior?

Thanks!