[Mimedefang] Problem with backscatter

[Steffen Kaiser]

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On Mon, 22 Mar 2010, Jakub Wasielewski wrote:

> It only occurs on backup MX server (sendmail 8.14.0) who checks for
> valid recipients using
> md_check_against_smtp_server().

Why does the mail hit your backup MX in the first place? Is the primary 
server offline?

> The problem is that a DSN message is generated and sent to
> victim at email.com about message

Did you verified that the DSN is from one of _your_ hosts at all? IMHO 
there should be a:

sendmail[pid]: queueid1: queueid2: DSN: reason

log entry. Can you verify that queueid1 is the queueid of the message that 
entered your host from outside.

Regards,

- -- 
Steffen Kaiser
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