On Mon, 2012-04-16 at 08:34 -0500, /dev/rob0 wrote: > On Mon, Apr 16, 2012 at 07:58:31AM +0100, Sam Jones wrote: > > A bit of an extreme example, but i've often wondered, when > > looking through my Postfix logs, why some senders do this: > > > > Received: from mx-out.facebook.com (outmail019.snc7.facebook.com > > [69.171.232.153]) by ..... > > > > The connecting host has HELO'd as 'mx-out.facebook.com' > > If it is traced through in DNS: > > mx-out.facebook.com: 69.63.179.26 > > 69.63.179.26: mx.snc1.tfbnw.net. > > mx.snc1.tfbnw.net 67.231.153.30 > > 67.231.153.30 mx0b-00082601.pphosted.com. > > mx0b-00082601.pphosted.com. 67.231.153.30 > > > > What I find a little crazy is why this bears no relationship to > > the connecting IP, and its reverse DNS: > > > > 69.171.232.153 - matching, as shown, outmail019.snc7.facebook.com > > > > I'm just wondering as to what circumstances would lead to a host > > HELO'ing with a hostname that differs from the connecting IP and > > host. > > Possibly the sending MTA is behind a load balancer?
> > I'm sure it is perfectly legal, but I don't see the logic? > > I wouldn't do it that way ... I would have had all the load balancer > IP addresses resolve to the HELO name. But I have not managed a > project on the scale of Facebook, so maybe there is some other > consideration involved. Thank you rob0. Much appreciated. I did not considered the sheer amount of email they must emit and I guess some form of load distribution would be inevitable.
