Bug#988844: daemon_notifier_socket bind: Address already in use

[Chris Hofstaedtler]

Package: exim4-daemon-heavy
Version: 4.94.2-1~bpo10+1
Severity: important

Dear Maintainer,

thank you for maintaining exim, also in backports.

I have recently upgraded from the version in buster to
4.94.2-1~bpo10+1 from buster-backports.

Since then, on each service restart, I get this error in
/var/log/exim4/paniclog:
   2021-05-20 11:41:39.862 [1309224] daemon_notifier_socket bind: Address already in use

Specialities about this setup:
  /etc/default/exim4: QUEUERUNNER='separate'
exim4.conf is a custom config, diverged from the Debian config a
very long time ago.
An excerpt of maybe relevant options:
  exim_user  = Debian-exim
  exim_group = Debian-exim
  trusted_users = vmail
  never_users = root
  admin_groups = adm
  keep_environment =
  exim_path = /usr/sbin/exim4
  spool_directory = /var/spool/exim4

I guess upstream ticket 2616 could be used to mitigate this issue,
if the startup scripts set the new option when QUEUERUNNER=separate:
  https://bugs.exim.org/show_bug.cgi?id=2616

Please consider applying and using the upstream patch on top of
4.94.2 for bullseye (and maybe buster-backports).

Chris