The email that you send and then realise that someone was copied in who shouldn't be.
Don't you think Karen is a total slut?
Failmail is the pinnacle of failure or the result of a consistant string of failures and is often used to describe someone else's helpless situation
"He's got failmail!" to describe someone in the process of failing
in a different context "What's wrong with him?" "He just recieved some failmail" or "some failmail just arrived in the post"
or can be used as an insult; "Thats a terrible idea, check your inbox for some failmail you bad"