[development] internal messaging among users for Drupal 6.x?

[zeljko blace]

Hi folks!
Not sure if this fits support or development...sorry for cross-posting.

What is the logical solution to providing interface for internal
messaging among users for Drupal 6.x?
I need just basic inbox & outbox view,
and compose, reply & forward forms.

Is there a specific Module? something being ported from 5.x or made new for 6.x?

Regards - Zeljko