A Validator widget can help you check. You'll have the 'address' as a STRING input, and use an expression like:
The first slash starts a RegExp, the first period means 'match any character', the at-sign means 'match an at-sign', the second period means 'match any character', the second slash ends the RegExp, the third period separates the RegExp from its 'test' member function (which takes a string argument and returns true if the argument is matched by the RegExp), and the 'address' is the input variable.
Validating that an email address is 'valid' is generally impossible without actually trying to send something to the address. The best you can hope for is usually just to see that it contains an at-sign.