Blocking MX query

Ibrahim ibrahim1 at
Wed Sep 5 02:57:32 UTC 2012

All, thanks for the input and comment. In summary, I will block TCP port
25. My DNS loadbalancer (F5) can filter MX query and need license to do it.
But given the information the botnet use  address list with
pre-resolved IP addresses then blocking MX query is not the answer :-)

Thanks & Regards

On Wed, Sep 5, 2012 at 9:18 AM, George Herbert <george.herbert at>wrote:

> On Sep 4, 2012, at 12:07 PM, William Herrin <bill at> wrote:
> > You are. You should be doing SMTP Auth to *your* email server on which
> > you have an authorized account and then letting it relay your messages
> > to the world.
> This is not the thread for this conversation per se.  The practicality of
> general ISP 25 blocking is established for antispam purposes.  So are power
> users running home domains.  Different user profiles.  Different
> circumstances.
> George William Herbert
> Sent from my iPhone

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