Generated form's enum field does not accept email address in Id field


I’m trying to create a drop-down on a generated form with a list of email addresses. However, the enum Id field does not accept an email address. How can I escape the @ in the email address or work around this limitation?

Thanks so much.

Work around:
1 Replace the @ with ATCHAR


2 Then define an end execution listener on the task to replace the ATCHAR again with @

Is there a better way of achieving this?