[Gllug] Guarddog firewall question

Chris Bell chrisbell at overview.demon.co.uk
Sun Jun 11 10:03:43 UTC 2006

On Sun 11 Jun, Casper Gasper wrote:

>  Is it?  If the OP is sending mail, the connection is made /from/ the
> local zone to the internet.  I'm not familiar with Guarddog, so maybe
> you're right and I'm mis-understanding this.  To put it in
> iptables-terms, the port hole needs to be on the OUTPUT chain, not the
> Casper.

   SMTP delivery requires the destination to be open to receive mail as it
appears, which is generally not the case because only a relatively small
number of end users run their equipment 24/7. This means several retries,
and repeated server effort, to deliver the average email. Also junk mail and
other nasties are easily posted to an open port 25, so many ISPs allow their
customers to access their mail via something like POP3 but block SMTP port
25 delivery. SMTP mail from their customers is not affected, the ISP does
aim to run 24/7 but not continually poll their customers via POP3.

Chris Bell

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