Meaning – The term permanent error, refers to an error that cannot be resolved by error recovery programs.
Permanent errors indicate when the recipient’s server returns the email to the sending server. This usually applies when the address of one or more recipients is no longer active and therefore can’t receive messages anymore.
Other reasons for this may include:
Invalid email: when the email address of one or more recipients is missing, has been canceled, or is false;
Inbox: when the server doesn’t find the recipient’s inbox, which can no longer exist;
Syntax error: when the email domain provider finds not allowed characters or blank spaces, indicating an error in typing;
Returned: when the server receives the email, recorded as delivered, but in a later submission, it can’t find the mailbox and then returns the email.
Example of usage – “Due to problems in the email server, she was unable to send emails to her colleagues and had to call them on a conference call to tell them the new updates.”