Re: [exim] configuring multiple MTAs

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Συντάκτης: Leonardo Boselli
Ημερομηνία:  
Υ/ο: exim-users
Αντικείμενο: Re: [exim] configuring multiple MTAs
On Thu, 29 Jun 2006 jori.hamalainen@??? wrote:
> > Do I have to run a DNS (BIND) on each machine?
> No Bind is needed unless you want MX based routing.


I suppose you wnated to say the reverse of it:
Bind is not needed unless you want MX based Routing.
I add: since in your plot there is the event that one or more hosts are
not directly reacheable, there is also the possibility that also DNS are
in the same situation.
So keeping a bind on each host is a safety net. 
I would use the MX way.
I would put all hosts in the mx list, wit lower numbers given to those
that have more possibility to connect to end one.
The actual arrancement has nothing to do with uucp and other serial point
to point intermittent connection.
I was working just yesterday in a net that has the same problem (not
every pair of hosts can connect directly and some ones are intermittently
connected).
Only trouble, for wich i ask to experts since it would requiere a exim
config tweak:
Suppose:
host5 MX 1 host5
host5 MX 10 host4
host5 MX 15 host3 
host5 MX 20 host2
host5 MX 40 host1
if i send from host1 and i am unable to connect host5 i would follow
trying with host4. suppose i pass the message to host4, but this one in
turn is not able to connect to host5, that at the time can reach only
host2.
The should a way to tell the MTA that:
 if ((I have the mail queued for more than 21 hours) and
     ( I am an _intermediate_ MXchanger ) and 
     ( I am unable to connect any lower MX or they refuse e-mail er.454)) 
 then
     {
       flagh the domain as unreacheble for 21 hours and return a 454 error
           should more messages for the domain arrive unless
           such mail is generated locally;
       pass te message to the next reacheable MX _up_ in the list;
     } 


In this case our message would be sent back first time to host3, next to
host2 that in turn would send to host5.