Hi all,
as some of you may already know, I spend a fair amount of my time
trying to help end users who are new to Exim or postmasters who are
converting from other MTAs to Exim.
I'm in the middle of some documentation at the moment and have hit a
brick-wall. Rather than just make a snap-decision on how to progress I'd
be interested in the advice or opinions of others in the list.
Based on the good advice I received form Tony Finch and others on the
list I am using IP addresses in the range 192.0.2.0/24 (from RFC 3330)
in my examples.
In my examples I am using the following domain names:
local-domain.example
relay-domain-one.example
relay-domain-two.example
external-domain-one.example
external-domain-two.example
local-domain.example is delivered to a local mailbox on the Exim server,
so no problems here.
relay-domain-one.example and relay-domain-two.example are both delivered
by a manualroute router, so again no problems here.
However external-domain-one.example and external-domain-two.example are
to be delivered by a dnslookup router. Now that I am using the
192.0.2.0/24 range I can no longer use dnslookup to route messages as
the Exim servers in the examples can no longer contact any DNS servers
(Yes I understand the irony of creating an isolated network then being
surprised that I can no longer query DNS servers).
RFC 3330 says:
192.0.2.0/24 - This block is assigned as "TEST-NET" for use in
documentation and example code. It is often used in conjunction with
domain names example.com or example.net in vendor and protocol
documentation. Addresses within this block should not appear on the
public Internet.
I Would like to keep the 192.0.2.0/24 addresses but I would also like to
be able to have a dnslookup router for showing how dnslookup deliveries
work.
I've been asking myself these questions over and over:
1) How important is it to use 192.0.2.0/24 addresses (so they don't
cause conflicts with other systems)
2) How important is it to be able to query a real DNS server when
explaining a dnslookup router? I could either include instructions for
builing a fully-functional DNS server on my "TEST-NET" which would
provide DNS info for the two external domains to Exim, or I could just
use could an existing hotmail or gmail account to prove the external
deliver works as advertised.
3) Is it possible to fake an MX lookup without actually using a DNS
server. Can I give Exim hints whilst still using a "dnslookup-stlye"
router that is still useful as an example?
4) In desperation,I have been trying to force Exim to look at my
/etc/hosts file to resolve the MX lookup using the following options:
dns_again_means_nonexist (should this be dns_again_means_nonexist = *)
srv_fail_domains = *
mx_fail_domains = *
and a hostfile with entries like this
192.0.2.100 external-domain-one.example
192.0.2.200 external-domain-two.example
Either I'm doing something wrong or this "fallback when no MX record
exists" only works for a real DNS A record and not just an entry in a
host file.
Sorry about the length of this message (I don't ever remember anyone
being told that they had sent too much information to this list, only
too little).
ANY help/opinion/advice would be appreciated
How would you guys go about doing this?
Thanks
Jason_Meers
--
website at:
http://www.exim-new-users.co.uk
hosting by:
http://www.line3.co.uk
