Forcing Sendmail to close connection (was Re: [Mimedefang] Blocking spam senders using IPTables?)

David F. Skoll dfs at
Wed Nov 3 10:22:05 EST 2004

On Wed, 3 Nov 2004, Aleksandar Milivojevic wrote:

> This is because we have only "error" built-in mailer in Sendmail.  If we
> had "disconnect" built-in mailer, things would probably be a bit different.

>From reading the Sendmail source code, it looks like Sendmail 8.13.1
treats a 421 reply code from a milter "magically", and shuts down the
connection.  See line 3376 of sendmail/milter.c and line 848 of
sendmail/srvsmtp.c.  I do not believe this "feature" exists in Sendmail

It looks like some rule sets can also force the connection to be terminated
by returning 421.



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