Re: [courier-users] Filtering question ...

Thomas von Hassel wrote:

> Ok, let me se if i can explain this:
> This is my setup:
> internet ----> filtering server ----> mail server (courier)
> I want to stop mail from going directly to the mailserver. Some
> viuses apperantly do something like this
> take xxx@domain.com and try deliver it firectly to
> [pop3,mail,etc].domain.com
> Under other cirumstances i could just firewall the mailserver to onyl
> accept incomming mail from the filter, but this server is also in use
> as an outgoing smtp relay for my customers. Now, how do i filter/
> ristrict my mail flow, so that mail from the filter and mail from my
> clients for relay get acceptet, but mail from the outside to the
> domains hosted on the mail server get's bounced, or redirected to the
> filter ?
> I hope i made myself clear .. any suggestions on how to do this in
> courier ?

If the filter server can be configured for SMTP Authentication, you can
set AUTH_REQUIRED=1 in /etc/courier/esmtpd. Then the mail server will
only accept SMTP mail from authenticated clients (you're relay customers
better already be doing SMTP Auth, otherwise your an open proxy). If
this won't work, another possibility is to firewall off (or even disable
courier from using) port 25. Configure the SMTP filter and all relay
clients to connect to SMTP-SSL port 465 or SMTP-MSA port 587 (make sure
you've turned these on on the Courier box. Have fun.

Jay

--
Jay Lee
Network / Systems Administrator
Information Technology Dept.
Philadelphia Biblical University
--



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