If you are a Project Owner and would like to continue communication with Vendors, as long as the Opportunity Q&A end date is set to never or set to a date after the Project closes the Opportunity Q&A functions the same, even after the close date has passed. 

For more information about setting up the Opportunity Q&A click here. 

If you are a Vendor and would like to use the Opportunity Q&A to reach out to the Project Owner click here.