-----Original Message----- >From: Alessandro Vesely [mailto:ves...@tana.it] >Sent: Friday, September 24, 2010 2:40 AM
>> In my experience, enterprises of size actually operate dedicated boundary >> servers as their MX platforms, and final delivery is handled by an entirely >> different set of servers often totally invisible to the outside user. >While that's correct, those invisible servers are not _primary_ MXes >on the public Internet. So, it is still unanswered why large >enterprises may want to operate _secondary_ MXes, i.e. MXes with a >higher preference number. Ummm... the "invisible servers" are not actually any kind of MX on the public Internet, primary or otherwise. There is a certain amount of confusion in this area because a lot of the mindset is structured around the notion that the "primary MX" is final recipient (the MDA), and other MX nodes end up relaying traffic to that "primary". But if you use a purpose designed "boundary server" whose sole job is scanning and filtering, then forwarding the scanned mail to distinct delivery nodes, you may well choose to implement multiple such systems attached to different network providers and/or points-of-presence. In this model, the MX is just another MTA, quite distinct from the MDA and MSA. For example: suppose you have campuses in Los Angeles and New York. Each campus has its own connection to the Internet, but also a private network between the two. Even if you want the bulk of outside traffic, and all mail, to go to LA, it may make sense to have an MX based in NY with a lower priority that routes its traffic to LA over the private network. That way a service outage on the LA campus would not bring down all external mail acceptance. I don't think we're in disagreement with anything, here, other than perhaps the issue created by the fact that "MX server" has been conflated with "delivery server", a fact that should surprise no-one who's seen the separation, over time, of the MTA, MDA and MSA parts of the system. Malc. ------------------------------------------------------------------------------ Start uncovering the many advantages of virtual appliances and start using them to simplify application deployment and accelerate your shift to cloud computing. http://p.sf.net/sfu/novell-sfdev2dev _______________________________________________ courier-users mailing list courier-users@lists.sourceforge.net Unsubscribe: https://lists.sourceforge.net/lists/listinfo/courier-users
