On Sat, 2009-12-05 at 14:02 -0800, Andrew Danneffel wrote:
> Hi there,
>
> My Blue Quartz server is constantly being hammered with email to users
> that do not exist on the server (I believe they are referred to NDRs).
> The maillog lists thousands and thousands of these "No such user here"
> errors each day. Strangely the vast majority of them are to two
> domains, each which start with "a". I don't believe the server is
> automatically sending out responses to these senders as this has been
> happening for some time and the server is not blacklisted from what I
> can see. I understand that these messages are from spammers and that
> the sender email addresses are spoofed.
>
> I am wondering what (if anything) can be done to prevent the server
> from processing and logging all of these useless messages. I suspect
> all of these mail requests are generating significant data transfer.
> Is it simply a fact of life or can some component of the mail system
> be optimized to stop it?
>
Are you using any catchall email accounts?
If so stop using them!
Is you sendmail.mc / cf configured to accept unresolvable domains?
If so reconfigure
Also check if Sendmail configured for DNS-Based Blacklisting
Gerald