RikuS wrote:
iRedMail server tried to send this message for about next 20 hours without success, without any notification to user. Is this normal that local sender doesn't get any bounce message on this error?
This is normal because the recipient server sent smtp code '450' instead of '5xx'.
450 (4xx) means a temporarily issue and sender server should retry. 5xx means a permanent error and sender server should stop retry and notify sender.
So, it's a recipient server issue caused by its sys admin, not iRedMail.