Bug#990344: exim 4.94.2 update default configuration option breaks MTA

[sawbona at xsmail.com]

Package: exim4
Version: 4.94
Severity: grave

Half way through the update to exim 4.94.2, the installer pops up a 
warning in the terminal informing that the configuration file being 
installed is different to the one in place and prompts to choose 
what to do:

1. keep the installed configuration (default)
2. install the new configuration
3. check and compare the differences in order to choose.

In most default Debian installations the installer will be 
referring to the [c]/etc/exim4/exim4.conf.template[/c] which is used
by the default non-split configuration scheme used by most anyone 
running a Debian desktop box.

Most users will choose the (recommended) default option.

In doing so they will unknowingly break their exim4 installation.

The result is a non-working MTA, with system mail being held.
ie: not delivered to /var/mail/user folder while at the same time 
/var/log/exim4/paniclog slowly grows in size.

With all versions of exim previous to version 4.94.2 now rendered 
obsolete, exim 4.94.2 will break any and all configurations set up 
with previous versions of the package.

This happens whether it uses the default configuration ie: the 
non-split configuration scheme which uses the 
/etc/exim4/exim4.conf.template file or the split configuration scheme
used in more complex installations and which you can eventually opt 
for when installing Debian or by running dpkg-reconfigure 
exim4-config later on.

---

exim 4.94.2 is absolutely incompatible with any configuration files 
used/generated with versions previous to version 4.94.2.

Worse yet, it is absolutely incompatible with *any* configuration 
file contained in the exim-config package from versions preceding 
exim 4.94.2.

Presenting the option to keep *any* existing configuration file when 
updating to exim version 4.94.2 generates a big problem.   

---

Presenting the options to keep installed files is *always* quite 
reasonable but not in *this* very significant update.

Thanks in advance,