Nintex Promapp users email addresses have been changed when they haven't been edited by a Promaster. 

This occurs when the option SSO - Sync user details with SSO provider is set to ON in Admin > Configure > Security and the email address included with the SAML response from the identity provider is different to the email address stored in Nintex Promapp.

Turn the Sync user details option to OFF to stop the sync happening

OR

Ensure that the email address is mapped properly in the Identity Provider.