Zabbix sender timeout while sending

[Fixxxer]

Hello everybody!
I'm experiencing a strange problem with zabbix sender. When I send info locally (i.e. zabbix sender and trapper are running on zabbix server) it's ok. But when I try to send from other hosts to zabbix, zabbix sender times out like this:

[root@SL07500008003WS sbin]# ./zabbix_sender -z 10.75.0.140 -s HPServer -k ttest.key -o 123 -vv
zabbix_sender [14307]: Warning: Timeout while executing operation
Sending failed. Use option -vv for more detailed output.

All required ports are up and open.
What could be the cause?
Trapper is configured like this

[Fixxxer]

One more thing.
Tcpdump clearly shows that there's some sort of communication between sender and trapper.

[Fixxxer]

Problem solved.
It was firewall on the server side that was blocking port 10051.
Thanks everybody