==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version 0.9.9
- Installed with bash script
- Linux/BSD distribution name and version: Debian9.9 amd64
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MariaDB / Postfix / Roundcube / SOGo
- Web server (Apache or Nginx): Nginx
- Manage mail accounts with iRedAdmin-Pro? : No , Iredapd
====

Today i installed iRedmail 0.9.9 on Debian 9.9
Everything is working fine but  after a while  i opened SOGo , and noticed many SOGo messages, on this forum there is a solution described, thanks for that, but  in Debian Stretch 9.9 this solution will not work.

Solution for the newer Linux operating systems (systemD) is :
edit file :/etc/cron.d/sogo

and change this line from:
* * * * *      sogo   /usr/sbin/sogo-tool expire-sessions 60 > /dev/null 2>&
to

40 16 * * *      sogo   /usr/sbin/sogo-tool expire-sessions 180 > /dev/null 2>&
then : service cron reload && service cron restart ,  now the job is done at 16:40 every day instead of every minute

Also to keep log files a bit cleaner i changed  one line in /etc/rsyslog.conf

from:
#cron.*                          /var/log/cron.log

to:
cron.*                          /var/log/cron.log

save file and run :
/etc/init.d/rsyslog reload && /etc/init.d/rsyslog restart

voila, done smile saving disk space  wink