After add media type with own script i had problem with delivery messages to my communicator. So i tried to debug it and found where is problem:
Zabbix-server run as system user zabbix:
zabbix 21573 0.0 0.1 165016 3704 ? S 14:04 0:00 zabbix_server -c /etc/zabbix/zabbix_server.conf

when i add to my script lines:
echo ~ > /tmp/home.log
echo `id` > /tmp/whoami.log
echo `pwd` > /tmp/from.log
i saw that home is set to /root and script starts as user zabbix from location /
It's problem in two cases

• when you try to run from script some programs based on config files in your home directory - zabbix try to get /root directory and has no permission
• when you try to debug: simple > doesn't work because zabbix usually has no permissions to write in / (and > ~/file.log not working because ~ is /root)

Temporary solution, add to script:
export HOME=/real/zabbix/home

Expected solution: run scripts as zabbix user with zabbix home.