Is there any way to do an email blast to past guests with OR?
Sort of, but it's clumsy and not recommended. OwnerRez is not really designed as a bulk email marketing program. Instead, we recommend exporting your guest list from CRM > Contacts, or a specific sub-set of guests using the Booking screen, List view, Filter, and Export. Then, import the resulting Excel file into a bulk email marketing program such as Constant Contact or MailChimp.