mail app not working

Hi all

The mail app on my mac is refusing to work. It keeps saying "Cannot send mail: The server “p01-smtp.mail.me.com” refused to allow a connection on the default ports."

I can access mail fine via my iPhone or via the iCloud website. Has anybody else encountered this problem?

Thanks,

Chris

p.s. I'm currently running OSX 10.8.3 will all software up to date