Re: [exim] Distributed Exim servers?

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Author: Philip Hazel
Date:  
To: Piers Kittel
CC: exim-users
Subject: Re: [exim] Distributed Exim servers?
On Tue, 18 Jan 2005, Piers Kittel wrote:

> I'm trying to set up a number of private networks across the UK, all
> connected to each other by VPN. The current number of networks would
> be 6, and I would like to have 6 Exim servers. I'm aiming to have a
> single email address for all networks - such as one user on Network 1
> would have joedoe@??? and one user on Network 3 would be
> janesmith@??? - so the Exim server on Network 1 would have
> joedoe's mailbox and user info, and the Exim server on Network 3 would
> have janesmith's mailbox and user info. Is this setup at all
> possible? or will I be required to seperate the email addresses such
> as joedoe@??? and janesmith@???? I
> suspect I can only set up one MX record on the DNS server and email
> for all networks would go through one exim server which isn't optimial
> (as bandwidth isn't that large)?


Logically, there seem to be only two choices

(1) As you say, having everything go through one server;
(2) Having every server know where the all mailboxes are.

The second could be quite feasible if you have some kind of distributed
database[*]. That would also allow you to do recipient verification at any
of the servers. The MX could point to all 6 servers. A typical message
would arrive, randomly, at one of them, and then be forwarded to the
correct one. Some messages, of course, would be lucky and hit the
correct server first time.

[*] which could be as simple as a file that is rsync'ed every so often.


-- 
Philip Hazel            University of Cambridge Computing Service,
ph10@???      Cambridge, England. Phone: +44 1223 334714.
Get the Exim 4 book:    http://www.uit.co.uk/exim-book