Re: Recieving email from aol or yahoo or hotmail, that is not addressed to me personally.

[Karsten Bräckelmann <gu...@rudersport.de>]

On Sat, 2011-10-15 at 16:39 -0700, Paul Cabot wrote:
> On 15/10/2011 3:39 PM, John Hardin wrote:

> > > Is there any way of blocking emails sent to me that are not really 
> > > addressed to me.
> >
> > ...you don't ever want to receive legitimate BCCs?

Or these very list posts, addressing the question at hand.

> Didn't think about the fact that it would be because of me being a BCC.

There seems to be a misconception, about what the visible mail headers
like To and Cc actually are. Feel free to slap me, if I'm wrong. :)


The most important thing to understand is, that both the To and Cc
headers are really merely cosmetic. They don't mean anything, as far as
SMTP (transferring mail) is concerned.

Given a regular MUA, the whole bunch of To, Cc and Bcc take addresses
the mail should be sent to. The distinction between To and Cc mostly is
pleasing the human old-school behavior. With email, the Cc is not really
a carbon-copy as in it's original meaning, and unlike a physical letter,
there can be more than one To addresses.

The Bcc header is different, in that it means the MUA and MTA are
supposed to not display and tell them to others, and basically every
software today adheres to that. Most handy for mass-mailing your friends
without leaking the whole list to everyone (and getting floods of
inappropriate Reply-To-All back later).


The other piece of the puzzle is the Envelope From -- the address(es)
actually used in SMTP, denoting the recipient address. From a user's
POV, that's To, Cc and Bcc combined.

>From the SMTP POV, the Envelope From is all that matters, and not
necessarily the same as these headers. In fact, that stage of SMTP is
done entirely before *any* mail header gets transferred. Hence the
"envelope". That stage is early in the SMTP session, way before these To
and Cc headers are being transmitted at all.

To complete this picture: The To and Cc headers are *inside* the
envelope, right on your letter. The actual list of recipients is given
to the postal worker, along with an appropriate number of sealed
envelops...


-- 
char *t="\10pse\0r\0dtu\0.@ghno\x4e\xc8\x79\xf4\xab\x51\x8a\x10\xf4\xf4\xc4";
main(){ char h,m=h=*t++,*x=t+2*h,c,i,l=*x,s=0; for (i=0;i<l;i++){ i%8? c<<=1:
(c=*++x); c&128 && (s+=h); if (!(h>>=1)||!t[s+h]){ putchar(t[s]);h=m;s=0; }}}