Blocking MX query

Ibrahim ibrahim1 at gmail.com
Tue Sep 4 05:24:47 CDT 2012


Hi Suresh,

We create special NAT that all destination use TCP port 25 will be NATed to
one public IP address only. And this public IP address is registered on
most of RBLs. But we are still receiving complaint about spammer from this
public IP address :-)


Regards
Ibrahim

On Tue, Sep 4, 2012 at 5:12 PM, Suresh Ramasubramanian
<ops.lists at gmail.com>wrote:

> Feel free to block port 25.  Most if not all mail providers offer
> email access on webmail and on an alternate smtp port (587)
>
> If you have NAT - the problem is that if you have spammers abusing
> your service (or abusing other services on port 25) providers will end
> up blocking your NAT gateway IP and then you have a problem.
>
> You will want to look at walled gardens or similar to block spamming /
> infected users.
>
> Please see the maawg best practice for walled gardens and port 25
> management.
>
> On Tue, Sep 4, 2012 at 3:37 PM, Ibrahim <ibrahim1 at gmail.com> wrote:
> > Hi All,
> >
> > I've read old archive about blocking SMTP port (TCP port 25). In my
> current
> > situation we are mobile operator and use NAT for our subscribers and we
> > have few spammers, a bit difficult to track it because mostly our
> > subscribers are prepaid services. If we block TCP port 25, there might be
> > "good" subscribers will not be able to send email.
> > We are thinking to block MX queries on our DNS server, so only spammer
> that
> > use their own SMTP server will got affected. All DNS queries from our
> > subscribers already redirected to our DNS cache servers. But seem Bind
> > don't have feature to block MX query. Any best practice to block MX
> query?
> >
> >
> > Regards
> > Ibrahim
>
>
>
> --
> Suresh Ramasubramanian (ops.lists at gmail.com)
>


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