Re: [exim] Double outbound routing for testing purposes

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Author: Andrew C Aitchison
Date:  
To: Johnnie W Adams
CC: exim-users
Subject: Re: [exim] Double outbound routing for testing purposes
On Mon, 15 Jun 2020, Johnnie W Adams via Exim-users wrote:

> Hi, folks,
>
>     I'm moving out some old Exim nodes and moving others in, and it
> occurred to me that if I could doubly route traffic from our sending
> receivers, I could direct a production stream at a machine in testing and,
> so long as I had a freeze filter or something similar to keep mail from
> leaving the machine being tested, I could see how the new node would handle
> inbound mail.

>
>     This seems obvious, but I can't find examples or instructions, so
> maybe it's a bad idea. I'd love to understand why--or how to do it, for
> that matter.


I doubly routed *incoming* traffic the first time I replaced our
exim server box - c2000, but not the second time.

Keeping mail from leaving the machine being tested was my main concern;
forwarding and rejecting/bouncing were the main problems, but IIRC
there were unexpected edge-cases too. I hadn't considered a freeze
filter, although that does make it hard to test some things ...

I started by routing just my mail to the new machine, so I knew that
the basic config was close to ready. I may even have moved users
to the new machine a few at a time ...

The second time I replaced the hardware I had more experience with exim
and less available time - more other things to do (rather than a
deadline for the switchover).

As a way of load testing the new setup it was useful.

-- 
Andrew C. Aitchison                    Kendal, UK
             andrew@???