I would like to attach a standard message at the end of my e-mails, below my name, something to the effect that if you have received this message in error please delete it immediately. How do I do this? I use BT Yahoo mail.
Log onto your email account then go to settings/options and scroll down and you should be able to find "signature" Add what you want and save. It will show up on all your emails.
This link is for Yahoo but should be more or less the same for BTYahoo.