The reply-to and from name on the Send User Name Autoresponder is configured on the following Site Setting (Setup > Site Options):

The name you specify for this site option will be displayed in the "From" field for email messages originating from your site. Luminate Online template macros may be used.

Advanced Site Administrators in Luminate Online will have access to this. If you cannot see it, please Contact Support, reference this article, and state the name you would like for it to be updated.