I just found out today that you can ‘Recall’ unread emails that you have sent in error.
I made a mistake and needed to correct the official email before resending so I followed this tutorial.
Long story short, it only works if you use MS Exchange and if the recipient has NOT read the email. IE, you have to do it quickly.
It will run through the recipients and let you know if it was recalled or not.
Hope this helps if you ever find the need to take back something you said or recall an official email.
M