zabbix problem with media types, no emails

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Hello,

I have a problem with the media types on my zabbix server. (Zabbix 3.4.4)

i configure auto registration for my hosts, everything works except the email notify. in the media types i configure the zabbix server to send emails.

if a host registration at the server admin notify by email, the host will add to server than add to a group, after this the host will disabled.

now i have found the problem, if i change in the zabbix_server.conf the value DebugLevel and restart the zabbix service everything works, and emails will be send. in the webinterface under Reports -> Actions Logs i can see that emails will be send but only if i change the value and restart the zabbix service.

# DebugLevel=0

to 

DebugLevel=4

on my test system i never change this value, but the test system is on Zabbix 3.4.4 but i don't think that there are many changes.

any ideas what i can do?

thanks for every help!

best regards and happy new year!