def unban(email):
    """Remove an email address ban.

        This removes a specific or global email address ban, which would have
        been added with the `ban()` method.  If a ban is lifted which did not
        exist, this method does nothing.

        :param email: The text email address being unbanned or, if the string
            starts with a caret (^), the email address pattern to unban.
        :type email: str
        """
