Re: [exim] DNS MX records

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Author: W B Hacker
Date:  
To: exim users
Subject: Re: [exim] DNS MX records
Tony Heal wrote:
> I am going to try and stand up a second email server. This server will start
> as a test server and then be moved into production. To begin with what I
> would like to do is set it up using the same email domain as my current
> email server and only have selected users ported over. Here are my problems
> with this.
>
>
>
> 1.    DNS MX records - How can I have 2 email server? I already have a
> second and third email server set up for mail bagging set at priority 10 and
> 20. Can I set up a forth MX with a priority between the first(5) and
> second(10) at say 7? Will this cause emails to first go to the primary email
> server (5) then if a recipient is not found try the second MX record(7)? I
> am not real sure how all this works.


Probably better and easier to either:

A) partition a single server by use of virtual users and routers. As you have
separate IP available, you can even use different 'races' of POP/IMAP daemons
as well as segregating smtp by IP (needs Exim 4.X for ease of setup).

If all are in the same <domain>.<tld>, OTOH, then you will need to rely on acl's
or routers to split them out by $local_part lookups.

B) use a single 'published' mx as a selective relay host, splitting traffic to
separate non-published back-ends via private addressing, optionally lmtp instead
of smtp.

Not hard to configure MUA to use different boxen for reading and sending.

> 2.    related to the first but a little different. Is there any way on a
> debian Linux system using a very old version of exim (3.35) to have a system
> user with no email address, so that I can set myself up on the test email
> system, or do I have to simply forward my emails.

>


Debian Linux users should read and heed Deb-specific docs, but the 'general
case' would be to NOT use the conventional system/alias lookups.

Either re-point that router to a specified flat file/DB/CDB or per-domain
dirtree of such of your own, separate from the default user sources.

OR - remove it entirely and go 'fully virtual' for simplicity - entering only
the subset of local/shell-account users that you wish to have 'inbound' mail
accounts.

Also *strongly* recommend upgrading Exim 3.X to current release.
Security, feature set, and availability of current support are the primary reasons.

Too few here remember 3.X and even fewer are interested in messing with its
configuration to do the unusual.

Bill