Bouncing mail on SMTP level - gateway machine

Hi,

Is there any patch that allows Qmail-SMTPD to look up the address of
the recipient by connecting to the server in smtproutes, and if the
address gives a 5xx response give a 5xx response to the client
connecting to the Qmail server? If not the server specified in
smtproutes then perhaps using a pre-configured server?

I am trying to avoid bounces going out of the network - currently the
main machine sends out 5xx responses, but Qmail will have to send
these to the sender (legit or not!).

Thanks.
Andrew.
--
Andrew Hodgson in Bromyard, Herefordshire, UK.
My Email: use <andrew at hodgsonfamily dot org>.

Andrew Hodgson wrote:

> Hi,
>
> Is there any patch that allows Qmail-SMTPD to look up the address of
> the recipient by connecting to the server in smtproutes, and if the
> address gives a 5xx response give a 5xx response to the client
> connecting to the Qmail server? If not the server specified in
> smtproutes then perhaps using a pre-configured server?
>
> I am trying to avoid bounces going out of the network - currently the
> main machine sends out 5xx responses, but Qmail will have to send
> these to the sender (legit or not!).
>
> Thanks.
> Andrew.

Andrew,

I have not heard of such a patch. Please note that an implementation of
such a thing might enable a DOS against your system and those behind it.
This would make the SMTP session extremely complex.
Essentially you are looking more for a proxy server then a gateway.
If the remote system already has the capability of rejecting a message
addressed to an unknown recipient, I do not see why a qmail server as a
gateway is needed.

I believe on www.lifewithqmail.org using the LDAP patch you might be
able to incorporate qmail with an AD setup (I did not tried so do not
know for sure) There are other patches that modify qmail-smtpd to check
for a local recipient before accepting a message. It might be possible
to consolidate multiple AD organization into your own local LDAP server.
Or simple have a defined list of acceptable email addresses.

But a lot more thought needs to be put into planning, setting up,
testing and implementing such a configuration.

If your system has qregex compiled in, you could reverse the behavior
for badmailto from rejecting email addressed to emails in the control
file to accepting them and rejecting everything else. I've done
something like that before. Simple alteration of the logic.

Please note that this will help spammers to identify valid email
addresses on your system/s.

AK

Andrew Hodgson wrote:

> Is there any patch that allows Qmail-SMTPD to look up the address of
> the recipient by connecting to the server in smtproutes, and if the
> address gives a 5xx response give a 5xx response to the client
> connecting to the Qmail server? If not the server specified in
> smtproutes then perhaps using a pre-configured server?
>
> I am trying to avoid bounces going out of the network - currently the
> main machine sends out 5xx responses, but Qmail will have to send
> these to the sender (legit or not!).

A SMTP callout can be done with the RCPTCHECK Patch (*). I use this patch by
myself to verify recipients against an internal Microsoft Exchange server.

(* http://www.soffian.org/downloads/qma...smtpd-doc.html).

--
Greetings
Jörg Backschues