mail client

I am asking this question here because I see many Drupal people using Macintosh systems. I am not a Mac user, but a client of mine is. He is currently using Entourage (came with Office 2004, 2008) to handle his email. It has been giving him lots of problems and he wants to consider other clients, and possible Gmail. He currently has email on his domain, but that can be redirected to a Gmail account.