I noticed something disturbing in my Postfix logs:

Someone addressed some spam to "sales@olib.org", it seems.  That didn't
exist, so Postfix replied "no such user".  But the sender disconnected,
and it appears that Postfix then tried to transmit the message in a
separate connection.

As it happens, the connecting IP seems to match what was used for the
attempted return-message.  But shouldn't Postfix have discarded the
message during the early SMTP handshake, rather than accepting mail
for an invalid user and trying to (re)send it?

This seems like it could be abused by spammers, and does not, by
my understanding (from memory) of SMTP, have to be done this
way.  In fact, the sender *should* see the failed RCPT: (or whatever)
command and that should be the end of it, by strict SMTP.  Sending
the message, anyway, after the RCTP: command failed was an error,
at which point Postfix was no longer obligated to do anything.

Even if this is "guaranteed" to bounce back to the sending IP,
and not some fake system, I'd rather not have the burden of carrying
email when the sender seems to blatantly break the rules.  (Yes, it's
a small burden.  For me, its principle.  For a larger system, it may
be a significant burden.)

Is there something that I can do about this, or am I misremembering
SMTP, and I should just let these things ride?


P.S.: On the subject of spam and ~invalid addresses, I originally
had the olib.org domain years ago, let it lapse, and repossessed it.
Much to my surprise, I've received some email to "aminet.uploader",
which *was* a valid address at one time.  (I uploaded a few small
things to Aminet, and constructed that address to handle related
contacts.)

I haven't used that address since those old days, but since re-
opening its mailbox, have received an occasional bit of spam.
Spammers must be desparate to hang onto, and keep using, an
email address for ~one decade even when the domain vanishes
for years.  (^&

(I intend to keep the domain this time around, but I find the
affair with aminet.uploader to be amusing.)


-- 
  "I probably don't know what I'm talking about."  http://www.olib.org/~rkr/