If you do not need your mail system to talk to the world, then you should
replace exim with something that is a lot simpler to use and configure. I would
suggest msmtp (https://marlam.de/msmtp/) as its configuration is a lot more
simpler to the neophyte. If you want to keep exim4, I would then suggest to nuke
the existing configuration and start from scratch with `dpkg-reconfigure
exim4-config'. Extended information should be available at
https://wiki.debian.org/Exim

Exim4 being a software designed to handle large amount of emails, it may be out
of scope for your personal usage. While, as I said, msmtp is a lot more
accessible through its minimalist approach: you only need a file with a dozen of
lines for it to function properly.

While I do use it, I wouldn't be able to help you with exim4, the software is
way too large and complex for my own understanding. I mainly rely on
dpkg-reconfigure and hope nothing breaks. And while msmtp is easier to
understand, changing software can itself be a source of immeasurable pain. So,
if in doubt, you should probably rely on dpkg-reconfigure.

Cheers,
                 Ludovic

On Wed, 01 Dec 2021, Marc Shapiro via Dng wrote:

>This is very likely the problem, as I now have version 4.94.2-7
>installed.  I know virtually nothing, however, about how MTAs do their
>work.  Where and how do I make these config changes.  I use
>Thunderbird for mail coming from outside the local network.  Exim is
>only used for local transport (such as e-mail from cron jobs).
>
>
>Marc
>