On Thu, Dec 04, 2008 at 10:15:55AM -0500, Sahil Tandon wrote:
> Gabriel Hahmann <[EMAIL PROTECTED]> wrote:
>
> > I'm new to the list and have a problem with my mail system. Recently I'm
> > receiving a lot of spam emails coming from the internet but the sender is a
> > user from my domain. Then I tried the same thing directly from other system,
> > as described below:
> >
> > telnet mailsystemwithproblem 25
> > helo testdomain
> > MAIL FROM: <[EMAIL PROTECTED]>
> > RCPT TO: <[EMAIL PROTECTED]>
> > DATA
> > test
> > .
> >
> > I've done this with success, and the machine that i've used to telnet is not
> > in the mynetworks or other parameter.
>
> This makes sense; MXs outside your networks should be able to send mail
> to your domains.
>
> > The problem is that all my users are receiving spam from themselfs. My
> > server is not an open relay because from outside I can't send email to other
> > domains, but if somebody connects and send to my own domain it works like I
> > said before.
>
> /etc/postfix/main.cf:
> smtpd_recipient_restrictions =
> ...
> reject_unauth_destination
> check_sender_access hash:/etc/postfix/copycats
> ...
>
> /etc/postfix/copycats:
> testdomain.com REJECT
>
> Be aware that your own users will not be able to send email to each
> other unless they're on mynetworks or SASL authenticated (both permits
> should precede the reject_unauth_destination directive).
Note that this will also block mail coming from your own users through
forwarders or mailing lists that do not rewrite the original sender.
(eg. [EMAIL PROTECTED] -> [EMAIL PROTECTED] -> [EMAIL PROTECTED])
Geert
