Checking for domain in email field - custom PHP rule

HI guys,

I'm new to rules an am stuck on an issue. I am using rules_forms to process some input from a form. I'll describe what I am trying to achieve and hopefully someone can help.

1) My client wishes to prevent any user with a free email account from posting through the contact form.
2) I have set up a rule that triggers on form validation and prints and error for the email field.

I tried to achieve the logic with text-compare, but it's not working for some reason , so I am going down the php route.

Essentially I have a regular expressions:

[a-zA-Z0-9_.]+@(gmail|yahoo|hotmail)(.[a-z]{2,3}){1,2}

That will check if the email contains, yahoo , gmail etc..

when setting up the rule with the text compare I was able to use the token: submitted[email] : to get the value of the email address.

In a nutshell, how do I access the value provided by this token in PHP so I can manually run my regex or any other logic against the email address field.

Any help appreciated, confused and frustrated - I haven't been able to find much documentation pertaining to forms/php with rules.

Many thanks

Hix