Re: [Exim] Re: Ho hum... Blackhole Lists...

On Tue, 2002-02-19 at 17:11, Philip Hazel wrote:
> On 19 Feb 2002, Dirk Koopman wrote:
>
> > And there is no 'better'[tm] way of doing it (for 3.3x) than:
>
> That doesn't do it!
>
> > reject_illegal_char_relay:
> > driver = smartuser
> > no_verify
> > condition = ${if match{$local_part}{[\\@%!/|]}{yes}}
> > new_address = :fail: rejected illegal character in local_part attempt
>
> That will fail those addresses with that error message when delivering
> messages that do not arrive over SMTP. (That is, locally generated
> messages.)

The specific problem I am trying to solve is this: my exim machine was
blackholed in orbz.org because the simple 'send_to_spamc' director was
passed the 'relay@???' in "relay@???"@localhost (that is:
BEFORE I added the above director).

It doesn't matter whether you set no_verify or not (on the spam assissin
director), it is still passed. Receiver_verify is on.

Now, can I say, that I am happy with my solution (I have taken the
no_verify out), it now rejects an "invalid" localpart at RCPT TO: time
with the above message.

IE:

mail from: <djk@???>
250 <djk@???> is syntactically correct
rcpt to: <"djk@???>
550 <"djk@???> rejected illegal character in
local_part attempt

I believe I have worked out what is happening normally here:-

1) email comes in that is potentially for a local doamin.
2) It gets passed out of exim to spam assassin to score.
3) spam assassin re-injects the messages as effectively a new message
but with a marker which says that it has been processed.
4) it is passed to the local director as normal.

BUT if the local part is a valid email address (eg relay@???), when
it is re-injected, it is treated now as *outbound* (because it is an
external address) and, of course, never sees any of the directors at
all.

Therefore, one way of dealing with it is: I clobber all messages, that
are potentially for a local domain, that have "dangerous" characters in
the local part before they are spam assassined or otherwise passed on.

What I haven't twigged yet is why % and ! are detected at RCPT TO: time
and not @. I thought @ was not a valid character in a local part.

Dirk
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