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Even with multiple domains you can still tell it to report an external ip if you like. The MX record doesn't have to even be accociated with the box OR network. It justs has to match up when a querry is made to your root domain. For instance my mail server is not even on the same domain, same city or same network but I report it is. :p
Aren't you the clever one.... :p
so let me see if I got this straight:
instead of the server doing the reverse dns check saying "hey...what is this ip address?" it says "hey...does this name and ip address match?" well...something like that.
In practical terms... Yes.. I think... I just don't _know_ it's a gut feeling...
Say you have a message going from mail server A that is 10.0.100.1 and you are saying this is a message from bubba.com. And itchy.com is reciving it. itchy.com says "what is the reverse dns on 10.0.100.1.?" Whoever owns that ip address has the authorty to enter anything they want into the RDNS record for 10.0.100.1 They own it. It can say blue.com if they want but if they do then forward and reverse records won't match because they don't own the authority for blue.com and reverse lookups on blue.com will always go to the authority for that domain.
but back on track
The authority for bubba.com (in tigers case his block from the ISP) will reply that 10.0.100.1 is mail.bubba.com. If 10.0.100.1 is accociated with multiple servers say bubba.com has a mail server on the ip and orange.com has a mail server on the SAME IP then additional info is needed. itchy.com's mail server will make the lookup with additional info. It will say 10.0.100.1 with a user name of billy is what? And the server with multiple domains will look for the user billy info and find a match and report the domain it is associated with.
here is an example, while not the same scenario is good reading.
http://www.sendmail.org/virtual-hosting.html
It is like, this packet says it is coming from domain A and the ip address is 1.2.3.4.Quote:
instead of the server doing the reverse dns check saying "hey...what is this ip address?" it says "hey...does this name and ip address match?" well...something like that.
What is the reverse dns record for 1.2.3.4 say?
if a match of domain A, good. 1.2.3.4 is coming from domain A. If they don't match or their is NO RDNS record, terminate connection and block ip 1.2.3.4.
//EDIT I guess this is a redundant post but simplified. I could have used beer cans instead of ip addresses. It is Bud in a class or Duvel?
In the 17 or so years I have been in the USA...
I'm still trying to decide if Bud is a beer or a joke on all Americans....
My gut says it's a joke... ;)
Laugh it up Tiger, when I was in London it was like 10 bucks a can. Back when a pint of English love was what,2 quid?
Brits secretly love bud. :p You think Bud is a joke? Ever tried Papst Blue Ribbon?
The _landlords_ love it at 2 quid a can.... Jeez... It's the kids thinking they are being cool. It's like some english beers... Bass comes to mind... It's like making love in a punt.... The closest thing to f*sking water.... ;)
Pabst, Schlitz, Coors, (with that _real_ mountain water), etc. etc. etc. The best beer you have here that I have tasted that is commonly available is, believe it or not... Rolling Rock... Yes, I'm a screw up... <LOL>
I like Rolling Rock. Sometimes a light bodied lager hits the spot. But I hang out at Rock Bottom Brewery. Local is the way to go. Just like England sometimes eh?