You have received a message saying "Delivery Status Notification (Delay)" after receiving a message.
You may occasionally receive a message looking something like below -
Delivery delayed: 'Original subject line of your email'
Delivery is delayed to these recipients or groups:
Email address(es) quoted here
The message hasn't been delivered yet. Delivery will continue to be attempted.
THIS IS A WARNING MESSAGE ONLY.
The server will keep trying to deliver this message for the next 1 days, 19 hours and 55 minutes. You'll be notified if the message can't be delivered by that time.
This message means that delivery of your email is taking longer than expected.
Likeliest cause - The recipient's email service is temporarily unresponsive or unavailable. Your email server will keep trying to send it for a set period of time. If possible contact the recipient by phone to find out if they are having email problems.
Also common - Was the email address of the recipient typed correctly or still valid? Please double-check your sent items for the message details. It may also be possible that that person is no longer at that organisation.
More rarely - This message can be caused if there is a backlog of messages on your email server which causes the queues to build up and emails such as this are sent out to let you know that things are running a little slower then normal.
Usually no intervention is required and the email will be received once the temporary problem is resolved.
If the server reaches the time limit (commonly 2 days) it will give up sending BUT you will receive an email confirming this. Normally this does not happen.
Very rarely do you need to resend it. Normally the underlying issue is fixed and the message arrives (albeit delayed). If not, you will receive a message advising you that the server gave up and the message was not sent.