Other - [PHP] Looking open source internal chat/message communication syste

Hi ,

My Requirement

Purpose : Internal staff communication using mail system ,

1.Compose message to other staff ,
2.View inbox mail ,
3.sent items,
4.reply options ,
5.instant chat with other user ,
6.Attachment supprt ,
7.Task assign

Is there any open will meet my requirement ,

Please share URL ,

Thanks

Bharanikumar