how to execute one playbook in all hosts at a time.

I have consists the following playbook.
But while executing playbook process happening is sequential manner.In this way for running one playbook for 30 hosts takes long time.I have tried with forks and serial parameters also. But nothing change i observed. The following is output of my playbook

ansible-playbook main.yml --limit test

PLAY [test] *******************************************************************

TASK: [mail | service postfix restart] ****************************************
changed: [srv613]
changed: [srv612]
changed: [dsrv143]

TASK: [mail | service dovecot restart] ****************************************
changed: [srv613]
changed: [dsrv143]
changed: [srv612]

TASK: [mail | service opendkim restart] ***************************************
changed: [dsrv143]
changed: [srv613]
changed: [srv612]

TASK: [mail | service apache2 restart] ****************************************
changed: [srv613]
changed: [srv612]
changed: [dsrv143]

TASK: [mail | service cron restart] *******************************************
changed: [srv613]
changed: [dsrv143]
changed: [srv612]

PLAY RECAP ********************************************************************
dsrv143 : ok=5 changed=5 unreachable=0 failed=0
srv612 : ok=5 changed=5 unreachable=0 failed=0
srv613 : ok=5 changed=5 unreachable=0 failed=0

So how to do this playbook running in all three hosts at a time?