Configure sendmail to reject mail for unknown users?

[Alexander Dalloz]

Am Di, den 14.03.2006 schrieb Timothy Alberts um 19:01:
> On Tue, 2006-03-14 at 02:26 +0000,
> replies-lists-redhat at listmail.innovate.net wrote:

> > are you sure there isn't an MX-record/host for the domain in question?
> > if it's "msiscales.com" there are two - so in that case, by the time
> > the mail reaches your internal mail server it's too late (you're
> > dealing with post-acceptance bounces, not bounces on delivery).
> 
> Yes, it is 'msiscales.com'. The second MX record is supposed to be a
> backup when our server is down.  The mail should be coming to us first,
> I think that's reflected by the priority within the DNS MX record.
> Which as you say, when our server goes down, all mail goes through our
> backup and we get bombarded with the spam and there's nothing I can do
> but try and filter it.  Under normal circumstances, all mail should come
> to the main server in question where I want it to be rejected.

$ host -t mx msiscales.com
msiscales.com mail is handled by 10 mail.adhost.com.
msiscales.com mail is handled by 5 12.98.95.107.

The primary MX (priority 5) entry is wrong. It has to be an A record.
Spammers nowadays mostly use the secondary MX host as that one is often
enough less protected than the primary MX. This way they can delivery
much more spam than normal. Probably you are now facing this by your
setup. The only way to avoid this is to have the very same anti-spam /
anti-virus setup on both the primary and secondary MX host.

Alexander


-- 
Alexander Dalloz | Enger, Germany | GPG http://pgp.mit.edu 0xB366A773
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