Layer 7 Load Balancer

Luc MAIGNAN luc.maignan at
Mon Nov 19 19:53:54 UTC 2007

Yes, you're true for the ip level. It's why I'm looking for a layer 7 
(application level) solution. For instance, I'm using postfix not sendmail.

Have you a postfix based solution ?

Les Mikesell a écrit :
> Luc MAIGNAN wrote:
>>>> My problem : I have two mails servers and I want to distribute 
>>>> incoming mails to a server depending of the domain (e.g. 
>>>> somebody at  to server1 and somebody at to server2)
>>> Uh, why?  Is there some reason DNS won't do what you need?  With 2 
>>> separate domains, just point your MX record to the correct server.
>>> Or am I missing something obvious here?
> > No, because the MX of the two domains points to the same IP (services
> > are dispatched behind this IP)
> Nothing at the IP level can distinguish inbound connections for the 
> different destinations and they are all going to be connecting to port 
> 25.  However, you can configure sendmail at that IP address (or 
> wherever you direct port 25) to accept for both domains and relay to 
> the other one at an address specified in mailertable.   The problem 
> you'll have with this is that the first machine won't know the users 
> on the other domain and will relay everything.  If you get a lot of 
> spam to non-existent users, then the real server will reject them and 
> the relay will have to construct and try to deliver a bounce, clogging 
> up your queues.  To avoid that you might use virtusertable to list all 
> the valid recipients at the other domain and a default rejection if 
> they don't change too much, or something like MimeDefang which can 
> check the real host for the recipient via smpt before accepting at all.

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