If you communicate via email with eBay marketplace Customers in Gladly, email replies to eBay marketplace could bounce if your company domain is not allowed by eBay. Incoming marketplace email subject lines usually follow this format below.
CUSTOMEREBAYUSERNAME has sent a question about item #, ending on DATE TIME - PRODUCTLISTINGTITLE
The failed delivery error will say, "Your message to CUSTOMEREBAYUSERNAME was blocked because it wasn't sent from your registered email address." If this occurs, contact eBay support and ask them to add your domain to their allowlist.