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Re: fooling MTAs.
On Wed, 27 Aug 1997, Peter wrote:
>
> >body and envelope
>
> Ok, I know that. And I can almost understand about the thing about the
> SMTP server friendlily warning about 'may be spoofed'. What I don't
> understand is, why does it accept the message if the From: domain is not
> the same as the IP of the incoming connection resolved by the name server
> ?! Normally I would enforce dropping connections with the From: domain not
> resolving to the sender IP (or an accepted sender from an ACL).
that would break many legit messages. for example, many people uses
virtual mail server, so the domain of the From is not the same as the mail
server's domain. another example would be a backup MX server that try to
send queued mail.
> Out of line: I was thinking about SMTP and long haul mail transmissions.
> You know, there is a thing called ping time, the time a radio signal
> requires to fly up and down to/from a sattelite or pass through zillions
> of wavelengths of fiber or copper wire. In SMTP the smallest number of
> question-reply pairs required to pass a connection is of 6. This means
> that the smallest mail message (null body) passes through a channel of ANY
> speed (no matter how fast) within MORE than 6*ping_time.
>
> If the ping_time is 0.3 sec (optimistical value over the Atlantic Ocean,
> i.e. from Israel to the States) then the shortest time required to pass
> an email via SMTP is of 1.8 seconds. With 10,000 messages to pass this is
> 18,000 seconds, 300 minutes or 5 hours.
>
yes, 10k messages is alot. but we have mailing lists to handle that
smarter.
> I infer that *NOONE* (sane) is using SMTP over long-haul. So what is being
> used ? A variation of UUCP batch mail over TCP ? BTW, noone could afford
> to send email if he had to pay for 1.8 seconds of sattelite channel air
> time for each message.
>
> subject for rumination....
>
> regards,
> Peter
> (plp@actcom.co.il)
>
Disclaimer: The opinions, ideas, thoughts presented here are my own
and do not reflect my employer's in any way
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