In this case it would suffice to notify the purported sender that
a message from them failed validation. It is not necessary to
quote any of the text of the message.
NOT if you are among those who believe the email is reliable
transport. Once your MTA has accepted
an email you are obliged to either:
1) deliver it
2) return it as undeliverable
If your understanding of English law is that you would be performing
a criminal act by doing so, then your duty to the Queen would surely
claim a higher priority than the mere opinions of this group?
One way that the spec could be improved would be to state that the
sender SHOULD notify the purported sender without mandating the
use of a particular mechanism, specify bounces as the fallback
mechanism.
Fine. But if you believe that SMTP is used for reliable
communication, you have to do *something*
with it.
Like fix the mess that is the SMTP spec.
What do you propose instead? Silently delete it?
Lets see, more than 90% sure its garbage, delete it unless the
sender suggests some other disposition.
Pass it off to the original recipients
postmaster? Neither is viable or acceptable in the context
of RELIABLE message transfer.
SMTP is not a reliable mail transfer protocol, neither as
originally described or as implemented.
The first step towards making SMTP reliable is to put authentication
in place.
The "culpable mental state" of Mens Rea is not applicable here:
1) We are bouncing BECAUSE we know the email to be bad with
reasonable high probability,
We have no specific knowledge that the email is pornographic.
Mens Rea is not applicable to inanimate objects such as computers
and statues and has not been since 950 or thereabouts.