On Sat, 13 Apr 2019, Rainer Dorsch via Exim-users wrote:
> Hi,
>
> I want to upgrade my server from Debian Jessie to Debian Stretch. I am afraid
> that at some time during the upgrade process, there is an invalid exim
> configuration and messages get rejected. In order to avoid that I was thinking
> of either redirecting via DNS to a server which does not listen to port 25 to
> enforce the sender to try again. Or redirect via DNS to a server which buffers
> all incoming messages until the Stretch setup is tested (not sure which server
> software does this though...).
>
> Can anybody recommend one of the approaches or even propose something
> better...?
I don't know Debian, but I'd hope that if you disable the service
it will stay off during and after the upgrade ?
Can you test on another machine ?
I've watched a process of redirecting the DNS while work was done on the
main server. You could set the backup server as an MX secondary.
You would probably want to manually switch this machine between holding
the mail and passing it to the MX primary.
Do you have a service-specific IP address, or does your current config
listen on the main machine IP address ?
I have to admit that I've always switched to new (or at least different)
hardware when doing a major OS upgrade.
If you can really afford to redirect to a non-listening server,
a similar option would be to do that at your firewall.
--
Andrew C. Aitchison Cambridge, UK
andrew@???
