Bug#921326: Bug#921205: Bug#921326: exim4-daemon-light: old exim4 daemon did not stop; socket bind() to port 25 for address 127.0.0.1 failed: Address already in use: daemon abandoned

[積丹尼 Dan Jacobson]

The problem only occurs during upgrades, not the daily boot. P.S., I
don't use testing. I use:
-- System Information:
Debian Release: buster/sid
  APT prefers experimental
  APT policy: (990, 'experimental'), (500, 'unstable')
Architecture: i386 (i686) (AND AMD64 too).