Hi,
I’ve 5 network devices which I wan’t to monitor “hostalives” (PING) on. I’ve them listed in the /etc/icinga2/conf.d/hosts.conf and they appear on the Icinga2 dashboard WEB GUI.
I read a little on the Monitoring Basics regarding the two e.x. scripts mail-host-notification and mail-service-notification. We’re running a O365 tenant, with the SMTP from O365.
Could I just add the following regarding mail listed in Configuration Mail: hosts.conf, users.conf, notifications.conf and templates.conf (hostalives)? I’ve added them now, and only changed the email = "%mail%" variable in users.conf.
What needs to be installed on the CentOS server first, before I can set this up? I guess there’s some requirements to get MAIL working? Like postfix/dovecot? 
Thanks in advance, this is so fun to learn!
Br
Magne