Re: [exim] configuring multiple MTAs

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Author: W B Hacker
Date:  
To: exim users
Subject: Re: [exim] configuring multiple MTAs
asutosh gopinath wrote:

> All my machines running Exim4 are on wireless lan. MTA1 may
> be out of range of MTA5 but may be possible that MTA6 is
> close to MTA5 and it may pass on the mail to MTA6. Knowing
> that the ultimate destination is MTA1, MTA6 can pass on to
> nearest MTA server and so on and so forth.
>
> This can happen at once or few of the intermediate MTAs will
> have to retry.
>
> thanks asutosh
>
>


Not a new problem. The 'net handles your attachment from any
supported POP to any valid IP, does it not?

Works for me when I cruise into, for example a Border's Book
store or Starbucks and connect via T-mobile WiFi to my own
servers in Hong Kong and Zurich.

What you want to do is handle that as a 'general case' TCP/IP
routing issue, and solve not only the Exim need, but also that
of web pages, file access, and all other networkish things, peer
to peer or to/from centralized servers.

IOW - relay the packets, not the mx identity. It should not be
an Exim issue at all.

Bill


>
>> ----- Original Message ----- From: "W B Hacker"
>> <wbh@???> To: "exim users" <exim-users@???>
>> Subject: Re: [exim] configuring multiple MTAs Date: Thu, 29
>> Jun 2006 14:43:52 +0800
>>
>>
>> asutosh gopinath wrote:
>>
>>
>>> Hi,
>>>
>>> I want to run exim4 in more than one machines in
>>> following manner:
>>>
>>>
>>> MTA-1 *   *    * *     *        * MTA-2  *  *  MTA-3  * *
>>>  MTA-4 *            *          * *        *   *      * 
>>> MTA-5   *    MTA-6

>>>
>>> User of MTA5 wants to send mail to user of MTA1. MTA5 can
>>> do it directly or can ask any one of the intermediate
>>> MTAs to pass on the mail so that it finally reaches MTA1.
>>> Say, for example,
>>>
>>> MTA-5--> MTA-6---> MTA-3---->MTA-2--->MTA-1 OR MTA-5--->
>>> MTA-3---->MTA-1
>>>
>>> Similar, if user of MTA-1 sends mail to MTA-5.
>>>
>>>
>>> Can this be achieved by Exim4. If yes then how do I
>>> configure all the MTAs? Do I have to run a DNS (BIND) on
>>> each machine?
>>>
>>>
>>> Please help
>>>
>>> Thanks Asutosh
>>>
>>>
>>>
>>
>> Yes but.
>>
>> Exim will ordinarily send directly to the destination MX if
>> it resolves and answers, and retry a lower-priority
>> secondary/tertiary/whatever MX - or the same route later
>> if/as/when it does not.
>>
>> Careful DNS crafting only solves part of the complex
>> routing for the diagram you propose. Crafting the
>> 'relay_to/from', retry and 'fall-back' rules for the
>> Tinker-to-Evers-to-Chance route can make your life
>> 'interesting' in a frustrating manner.
>>
>> Unless your network is Aloha packet Radio, RTTY or ARCnet
>> over a barbed-wire fence (don't laugh - both work), and/or
>> you expect to run around a million messages a day, this
>> should be more than slightly overkill. Not needed even for
>> cellphones or multi-continent hosts.
>>
>> ONE server can run multiple instances of Exim, but even a
>> single Exim can have highly flexible behaviour, handling
>> hundreds of domains, departments, or branch offices with
>> thousands of users each. Properly set up on either *BSD or
>> Linux, Exim is very hard to knock down, so ONE backup is
>> all most of us use.
>>
>> Cambridge and other Universities use Exim and some have
>> written up their systems on the web.
>> Multicollege/multi-campus universities are pretty demanding
>> environments, quite often justifying multiple servers with
>> different primary functionality, but, IIRC, still *much*
>> simpler, and dramtivally more smtp-compliant, than your
>> chart.
>>
>> ..or are you migrating off of 'bang-paths'?
>>
>> ;-)
>>
>> KISS (Keep It Simple, Stupid)
>>
>> Bill
>>
>>
>>
>> -- ## List details at
>> http://www.exim.org/mailman/listinfo/exim-users ## Exim
>> details at http://www.exim.org/ ## Please use the Wiki with
>> this list - http://www.exim.org/eximwiki/
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