This is a story I have heard from the coursemate of mine, I'll call her A. She has some issue to discuss with the dean, and since the dean was away, she decides to send her an email. She ends the letter with "Sincerely yours, A." Next day A checks her mailbox to find a reply from the dean that says :
"Dear A,
I hope you meant "sincerely."
Frantically, she opens her sent email, scrolls down... Apparently she has made a spelling error and the word automatically corrected it to - "Sinisterly yours"