How to customize a error message in sitecore 9 forms submit

If a submit action fails, for example if a form verification where a user already exists or a save action fails because an email could not be sent, the Web Forms for Marketers module displays an error message. You can customize the error message to ensure that the visitor receives the best possible information.

To customize a submit action error message:

1. In the Form Designer, open a web form.
2. Click the form's Submit button.
3. To customize an error message for a form verification or save action, on the left pane, click Form Verification or Save Actions.
4. In the Form Verification or Save Actions dialog that appears, on the Actions tab, in the Form Verification / Save actions drop down list, click and select the action that you want to edit the error message for and then click Add.

   

5. After you are finished with the selection, in the Form Verification or Save Actions dialog, click the Error Messages tab and enter the text of the new error messages for the actions you specified. Click OK.

   

If the submit action fails, the modified error message is displayed to the visitor.