Mail was successfully submitted for delivery but a copy has not yet been saved in your mail file due to server not responding

What happened

Mail is routed first and then saved. The server became unavailable before it could save the copy you asked for.

What you can do

If the mail document is still open and you want to save it, copy its contents to a document in a local application. If it's not open, ask someone who received it to forward it back to you.