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