A lot of times you get a form where you need to enter an email address (or other form field) twice in order to confirm that you typed it correctly the first time. Some forms disable the copy and paste action (via javascript) in the browser to force the user to type the email address again.
Personally I find this highly annoying. What are your thoughts? Are there other options?
If you really want to check the email address you could implement a confirm email address function, which sends an email to the provided email address. The email could contain a link which allows the user to confirm his/her email address.
For obscured fields like password fields, it is always best to implement a double entry input field in case the user made a typo.