Postifx as SMTP AUTH client

David-Paul Niner dpniner at
Mon Apr 10 20:30:09 UTC 2006

On Mon, 2006-04-10 at 15:33 -0400, Todd Zullinger wrote:
> Hash: SHA1
> David Cary Hart wrote:
> > On Mon, 10 Apr 2006 12:59:06 -0500
> > "J. K. Cliburn" <jcliburn at> opined:
> >> I'm pretty new to configuring mail servers, and I'm running into
> >> issues trying to get outbound mail to work.  I've configured Postfix
> >> to (I think) request smtp auth at my ISP's mail server in an attempt
> >> to get him to relay my mail, but I'm not sure the authentication
> >> attempt is happening.
> >> 
> >> A few background items...
> >> 1) PPPoE DSL connection, dynamic IP.
> >> 2) DynDNS/ddclient correctly working to keep domain name and IP
> >> address in sync.
> >> 3) Postfix on home LAN server correctly configured to send and
> >> receive internal mail.
> >> 
> > No offense but you should NOT be sending mail direct-to-mx from a
> > dynamic IPA. Many servers won't accept it anyway.
> J. K. is setting up his postfix to relay mail via his ISP.  This isn't
> much different a setup than a Mutt user would have or a Windows user
> might have where their antivirus software installs itself as an
> intermediary between the mail client and the real SMTP server.  His
> mail should go out via his ISP, pretty much like it would if he sent
> it directly via a client like Thunderbird.  How's that "direct-to-mx
> from a dynamic IPA"?

Your ISP's smtp server should be smart enough to recognize the
originating IP address as one your ISP assigned dynamically to your
client, and should allow the mail to pass after it passes any scanning
filters/white-black lists.

I agree with the assertion that it's bad policy to try to use other smtp
(that are neither yours or your ISP's) servers to attempt to relay mail
from DHCP-assigned IP addresses, public or private.


> - -- 
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David-Paul Niner, RHCE
dpniner at
Florida, United States of America

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