Steps to reproduce:
- Configure an auto-registration action to send notification about new hosts
- Create an host (i.e. "Server1"), and start monitoring it with agent-less checks, for example icmp ping.
- At some point, install zabbix agent on the target machine and configure with a slightly different Hostname casing (i.e. "server1")
Action gets executed every 1 minute, flooding email recipients.
Apparently it keeps firing because the host registration fails (it already exists with a slightly differente uppercase-lowercase combination).
Action is not executed at all, as zabbix-server should be able to matche new and existing hostnames using a case-insensitive criteria.