Re: [exim] maildirsize file and massive concurrency

On Sun, Feb 20, 2011 at 2:08 AM, Phil Pennock <exim-users@???> wrote:
> One approach might be to bias which hosts receive mail for a given
> mailbox; you said you had a two-stage system (good); so the front stage
> uses ${nhash_4:$local_part@$domain} to get a number 0-3; you use this to
> select which of the backing hosts is used, but set "fallback_hosts" to
> the complete list of backing hosts, so that in the event of a machine
> failure you still get delivery.  Thus normally all mails for one address
> go to just one host and you maintain NFS cache coherency.

Ok, now single stage systems. I was going to make a router/transport
that would do use this hash selection method and do lmtp direct to
exim. Seemed like a good idea, but then I quickly realized that exim
can speak lmtp when sending, but it does not do lmtp inbound, stopped
me dead in the water. The only other option that I can see is to make
a hostlist of my exim mail servers, receive the email, but instead of
delivering locally, do the hash function to select one of them and
forward it to that one (doing the local delivery if it happens to be
itself). The only issue I can see with that, is that the quota isn't
checked until the second instance (if it's not the local machine)
tries to do the delivery. The resulting backscatter is what I'm
trying to avoid in the first place by having a single stage system.

Any suggestions or comments?

--
Regards...      Todd
I seek the truth...it is only persistence in self-delusion and
ignorance that does harm.  -- Marcus Aurealius