Man and machine (was Re: Is virus scanning interception?)

[Ken Brown]

Actually at that point I was thinking of the SMTP commands which are
part of the same datastream as the message text. The program receiving
the mail must read every byte to know whether that byte is part of the
command/response conversation or a user's message.

But it equally well applies to headers. Some of them are in effect
directives to server software, or are frequently interpreted as such. A
different protocol layer in effect, but stll including traffic data. For
example your message to which this is a reply includes "received:",
"Precedence:", and "x-been-there:",  headers, any of which might be used
by a server to stop loops, or to try to prevent embarrassing
auto-generated mail going to silly places. (Anyway, mail listmanagers
such as Majordomo are in effect part of the infrastructure)

Quentin was talking one layer nearer the user than even that - most
implementations of SMTP store content & header in the same text files,
(at least temporarily - even IIS/Exchange 2000 has a temporary SMTP
queue file outside the database) so you have to read each line to spot
the start of the next header block.

All of course irrelevant. Your mail is read, can be read, and will be
read, by software certainly, and by people if they have a mind to,
regardless of what the law says, so if you want to stop others seeing
it, encrypt. No-one can legislate to repeal the laws of mathematics.

Ken

Jon Ribbens wrote:
> 
> Ken Brown <k.brown@ccs.bbk.ac.uk> wrote:
> > Yes, but the mailer has to read each byte to know which is envelope and
> > which content.
> 
> No, envelope information is not sent as part of the message. You're
> thinking of the headers, which are.
> 
> On the other hand, MTAs often *do* look at the message itself,
> including the body, to do things like MIME auto-conversion.