Error: "Deferred - Delayed - Warning: message still undelivered after 4 hours, Will keep trying until message is 3 days old"

The defered error message means that our email server has tried to connect to your correspondent's email server to send the message but hasn't succeeded, but hasn't succeeded for an unknown reason.

This error message indicates that our server will continue to attempt to send your message for the time specified in the error message.

If this message still can't be sent when this time has elapsed, you'll be sent a final error message to notify you that it wasn't possible to send your message and that your correspondent hasn't received it.