Bug#921205: socket bind() to port 25 for address (any IPv6) failed: Address already in use: daemon abandoned

[積丹尼 Dan Jacobson]

Package: exim4-daemon-light
Version: 4.92~RC5-1

For the last two upgrades,
/var/log/exim4/paniclog:
2019-02-02 21:47:07 socket bind() to port 25 for address (any IPv6) failed: Address already in use: daemon abandoned

As we see from timestamps, it is upgrade related.
# ls -dog  /var/log/exim4/paniclog /usr/share/doc/exim4-config/examples/
drwxr-xr-x 2 4096 02-02 21:41 /usr/share/doc/exim4-config/examples/
-rw-r----- 1  117 02-02 21:47 /var/log/exim4/paniclog

-- debconf information:
* exim4-daemon-light/drec:

P.S., a cronjob then sends
exim paniclog on jidanni2.jidanni.org has non-zero size
to the user the next boot.