miniOrange has a solution that can verify your online leads for you with its 2 step verification process. This can prevent you from calling leads that are bogus and save you time and effort. You can use this to validate email IDs as well as phone numbers (mobile as well as land lines)
With minOrange Mobile Number Verification Service , you get
When we validate an email or phone number, we validate whether it meets certain requirements like every email should have an '@' sign and a '.' and every phone number should have a country code, area code and should be 10 digits long. Verification of that email or phone number is done by sending a six digit number to that email id or mobile phone (and in case of a land line, an automated call is made that speaks a 4 digit number) and we ask the user to enter the same number on a form that they see on their laptops or desktops. If they are able to write the exact number then we know that the phone number or email is a valid one. Hence verified that the user has access to the number he is entering.