--On 29 June 2006 02:22:58 -0500 asutosh gopinath
<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.
Erm,...isn't there a way that this can be solved at the network level, so
that if there's a path between two hosts they can still see each other -
even if multiple hops are required?
If the network topology is not static, I'd have thought wireless bridging
combined with frequent Exim retries would do the job. If it is static, then
maybe it's easier to solve the Exim routing problem than the bridging
problem, but solving the bridging problem would also enable other services
to operate over the network.
Here's an issue with a dynamic network topology. Suppose MTA 1 has a
message for MTA 3, but can only see MTA 2. How do you know that MTA 2 is
going to make contact with MTA 3 before MTA 1 does?
> This can happen at once or few of the intermediate MTAs will have to
> retry.
>
> thanks
> asutosh
>
>
>> ----- 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
>>
>>
>>
>> --
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>> ## Exim details at http://www.exim.org/
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>
>>
>
>
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Ian Eiloart
IT Services, University of Sussex
