Preventing backscatter with sendmail

[Steve Freegard]

Gareth wrote:
> Havent been following the spamassassin tread but for postfix to stop
> creating backscatter yourself use recipient verification.
> To remove backscatter either use the mailscanner watermark feature or if
> outgoing mail doesnt allways go through mailscanner then you can use the
> spamassassin 'vbounce' plugin instead.

For Postfix you should really configure and enable the 'verify' daemon
if the machine scans messages for non-local users.  See
http://wiki.mailscanner.info/doku.php?id=documentation:configuration:mta:postfix:how_to:reject_non_existent_users#using_smtp_recipient_verification

That will prevent *you* from causing backscatter.  Any time you accept a
message where an upstream SMTP server will do an SMTP 5xx rejection will
cause you to generate an NDR to the envelope-sender (invalid recipients
being the most common cause of this).

Cheers,
Steve.