From: Mail Delivery Subsystem To: Subject: Returned mail: see transcript for details Date: Wed, 14 Aug 2019 15:02:39 +0000 Embedded: unnamed The original message was received at Wed. 14 Aug 2019 15:02:39 GMT from (10.187.9.621 The following addresses had permanent fatal errors (reason: 550 Host unknown) Transcript of session follows ---- 550 5 1.2 Host unknown (Name server: : host not found)