Webform validation in drupal 7

Question

I want to add a validation to my webform where, the webform should accept email id once. If the user provides same email id again a message should be displayed saying "mail id already exist". Any go using web form validation module? Please give me suggestions.

Answer 1

If you are using the Webform module. Then do the following:

1. Add a field of type "E-mail"
2. Under the edited section of this field there is a section called "Validation" one of the options for this validation is "Unique"