I recently built a Nintex Form that included a field where the user was asked to fill in their email address. The form needed to verify that the user was entering a valid email address.

This can be accomplished using a Regular Expression in the settings of the form control.  Below are the steps and Regular Expressions I used for validation the email address entered.

1. Add a Single Line Textbox control to the form.
2. Open the Control Settings and expand the Validation section.
3. Change the “Use a regular expression” choice to Yes.
4. Enter the one of the regular expressions below in the “Regular expression” field.
5. Enter your custom validation message in the “Regular expression error message” field (for example, “Please enter a valid email address”).
6. Save and publish the form.

Below is the main regular expression I have used to validate an email address on a form.

(?:[A-Za-z0-9!#$%&’*+/=?^_`{|}~-]+(?:\.[A-Za-z0-9!#$%&’*+/=?^_`{|}~-]+)*|”(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21\x23-\x5b\x5d-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])*”)@(?:(?:[A-Za-z0-9](?:[A-Za-z0-9-]*[A-Za-z0-9])?\.)+[A-Za-z0-9](?:[A-Za-z0-9-]*[A-Za-z0-9])?|\[(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?|[A-Za-z0-9-]*[A-Za-z0-9]:(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21-\x5a\x53-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])+)\])

I have also used the regular expression below to validate an email address.  It’s much simpler but does not check as extensively for certain patterns.  It does check for a 2-4 domain extension after the period.

^([\w+-.%]+@[\w-.]+\.[A-Za-z]{2,4};?)+$

Kudos to Eric Harris for first sharing this in his post on the Nintex Xchange site: Simple email validation for forms