internal mail

hello,
i have installed drupal and now i'm looking for an internal mail system in drupal!
is there any module or etc. which can make us to have an internal mail system.i wnat one which is independent on gmail or yahoo etc. and it is just for our own site and just for our member in order to send message to each other and like gmail or yahoo they can have inbox,sent,trash and etc.

_{Edited by WorldFallz - moved to appropriate forum.}