I have 3 questions regarding checking handphone and email address

1) Say i enter helloy.yahoo.com to the textbox, how to check whether it is
a valid email address when i click on a button to send...

2) Same situation as the above, how to check whether the the user key in
the correct handphone number and length...

3) If the above two questions can be achieved, can it be possible to check
both email and handphone in one textbox when the user key in either
handphone or email...or is t better to spilt the textbox..

Thanks