Forum Post: Delivery has failed to these recipients or groups

兩個訂閱的帳號, 自10/1開始, 都無法將信寄出。 都出現 Your message couldn't be delivered because you weren't recognized as a valid sender. Make sure your sending address is set up correctly and try to send the message again. If the problem continues, please contact your helpdesk. 請盡快協助處理。