Hello List! I recently discovered some nasty backscatter technique which I don't know how to stop. It only occurs on backup MX server (sendmail 8.14.0) who checks for valid recipients using md_check_against_smtp_server().
The SMTP session looks like this: Connected to xxx.xxx.xxx.130. Escape character is '^]'. 220 my_backup_mx ESMTP helo example.com 250 my_backup_mx Hello example.com [xxx.xxx.xxx], pleased to meet you mail from:<[email protected]> 250 2.1.0 <[email protected]>... Sender ok rcpt to:<[email protected]> 554 5.7.1 <[email protected]>: Recipient address rejected: User unknown rcpt to:<[email protected]> 250 2.1.5 <[email protected]>... Recipient ok data 354 Enter mail, end with "." on a line by itself [message content] . 250 2.0.0 o2MBG5xt002795 Message accepted for delivery quit 221 2.0.0 my_backup_mx closing connection Connection closed by foreign host. The problem is that a DSN message is generated and sent to [email protected] about message can not be delivered to [email protected]. Why this message is generated and how to stop that? I must mention that this doesn't happen for local recipients. This happens only when message should be relyed and the recipients are checked using md_check_against_smtp_server(). Please help! I do not want to be a backscatterrer! -- Jakub Wasielewski _______________________________________________ NOTE: If there is a disclaimer or other legal boilerplate in the above message, it is NULL AND VOID. You may ignore it. Visit http://www.mimedefang.org and http://www.roaringpenguin.com MIMEDefang mailing list [email protected] http://lists.roaringpenguin.com/mailman/listinfo/mimedefang
