On Fri, 25 Jul 2003, D.M.Chapman wrote:
> # If it ain't for me, send it to the mail HUB
> hub_route:
> driver = domainlist
> transport = remote_smtp
> route_list = "* ukc.ac.uk bydns_mx"
>
> on many mail machines. This works well with <v4 and allows us to add/remove/
> generally fiddle with the mx machines as and when we want to. As this config
> is on many machines (including some that we don't have direct control over)
> it would be nice to replicate this functionality with Exim 4.
The precise functionality is, in effect, "route this domain as if it
were that domain". This is still on the Wish List (in fact, I noticed it
yesterday when I was reviewing the list).
I didn't implement it for Exim 4 because I felt that the second data
item in a router list should be a list of *hosts* - the idea is that manual
routing is where you manually arrange for certain domains to be routed
to certain hosts. Putting an email domain name there instead of a host
name felt wrong.
However, in the meantime, various ideas I've had about how to do this
better have never really worked out. :-(
It has just occurred to me that way round this is just to think of it
differently. If you think of "ukc.ac.uk/MX" (for instance) just as a
more complicated way of defining a list of hosts, it fits in better with
the philosophy.
You can probably do this already, in a roundabout way, by using the
dnsdb lookup and some magic to manipulate what you get back, but it is
hellish complicated, and I don't even want to try.
I therefore have this new proposal:
If an item in a list of hosts for the manualroute router is of the
form <domain>/MX then it represents the list of hosts defined by the
MX records for that domain, in the order defined by the MX preference
values. The use of this syntax implies "bydns" for this item, because
MX records can be found only in the DNS.
Come to think of it, a general feature "name/MX" meaning "the hosts to
which this domain routes by MX" might have other applications.
> A collegue (fresh from Philips Exim course :-)) has made some progress
> using lookup dnsdb but it still has issues and is nowhere near as flexible
> as the old bydns_mx option.
Agreed.
> RoundRobin dns doesn't have the priority control (list some machines more
> than once? Messy).
Agreed.
> A final option might be for us to patch the code ourselves to re-introduce
> this option.
Relax. I think I have just surrendered. :-)
I'll take a look at the code and see what seems like a nice way to go on
this one.
Philip
--
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
