Victor Duchovni:
> On Fri, Jun 18, 2010 at 10:30:35AM -0400, Phil Howard wrote:
>
> > > I am fine with the workarounds supplied and can see your point of view,
> > > although I can't agree with a loop detected that is not a loop, I see
> > > that it happens because inet addresses are mixed between instances and I
> > > have my view about wasting more public ip addresses to do this as I told
> > > before. That's all. Thank you all for your answers and comments. :)
> >
> > The original principle of the loop detection is based on where DNS MX
> > records would point to. That points to hostnames which point to IP
> > addresses. Port numbers are not part of it and are assumed to be the
> > SMTP port. How the detection is actually implemented could vary.
>
> Not really, for loop detection to be effective, it must detect
> cases in which remote domains specify unexpected MX records (even
> 127.0.0.1) or local transport tables are incomplete. When MX records
> are bogus our transport tables are incomplete, the traffic will go
> to port 25, so all port 25 connections must be tested.
>
> The supported way to avoid loop detection false-positives on with
> internal forwarding between Postfix instances is to:
>
> - Ensure that each Postfix instance uses a separate set of
> IP addresses.
>
> and/or
>
> - Not use port 25 as an internal forwarding destination when
> IP address sharing is unavoidable.
>
> This is robust and easy to document. The work-arounds I posted
> also work, but are less elegant and should be avoided. If the
> OP wants to use them, fine, he is fully informed...
I recommend a different myhostname per "port 25" instance. The
Postfix SMTP client verifies the HELO response and will declare a
loop when the best MX host replies to HELO with the client's own
myhostname.
Wietse
