help setting up a mail server

i am admining a new website and we have a dedicated server that we admin ALL of it ourselves so there is nothing but an os on this box. i have php, apache, mysql and phpmyadmin all installed and working beatifuly, now i need a good and easy mail server for our needs. does anyone have any experiance setting one up and can point me to a EASY mail server app i can set up? we would like to use smtp and have webmail access if possible, but if not the staff can use outlook or thunderbird to access mail. we just need a server that our forums can send mail from and that is secure and you guessed it, EASY to use.

any help is appreciated.

note: this will be my first time ever setting up a mail server so be gentle.