[cse491] From address fail

C. Titus Brown ctb at msu.edu
Mon Sep 28 18:38:21 PDT 2009


On Mon, Sep 28, 2009 at 09:20:11PM -0400, Jack Carlson wrote:
> Ahh, thanks, got it.
> 
> Does anyone know what the MAIL FROM line is actually for, then?

That's the user actually responsible for sending the e-mail, as opposed
to the user advertised as sending the e-mail -- a fine distinction ;).

The MAIL FROM address is used in combination with the RCPT TO by the
server to determine if the server should accept the e-mail for further
processing.  An example set of rules used by most mail servers is:

 - do I know the MAIL FROM address?  If yes, then it's authorized to
   send e-mail through this server.

 - do I know the RPCT TO address?  If yes, then I'll receive this
   e-mail.

 - if not, DIE DIE DIE.

--titus



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