-----Original Message----- From: Mail Delivery Subsystem [mailto:MAILER-DAEMON] Sent: 10 March 2020 19:01 Subject: Warning: could not send message for past 4 hours ********************************************** ** THIS IS A WARNING MESSAGE ONLY ** ** YOU DO NOT NEED TO RESEND YOUR MESSAGE ** ********************************************** The original message was received at Tue, 10 Mar 2020 15:00:07 +0100 from localhost.localdomain [127.0.0.1] ----- Transcript of session follows ----- 451 croit.io: Name server timeout Warning: message still undelivered after 4 hours Will keep trying until message is 5 days old