Ive just set-up an autohits script on my website. It all works great and everything, except the e-mail.

It has automatic e-mail for when people sign-up, passwords etc. The e-mails send fine to other e-mail addresses that I have (for my other sites), but they don't send to the main stream e-mails like hotmail and Yahoo.

I can send mails from the back-end php admin however it says 'e-mail sent' but nobody receives them.

Anyone any ideas please cuz im confused

You'll probably find them in the spam folder

also make sure you add headers to your email.
A lack of headers is usualy the reason emails sent with php get binned.