How does one pull a sent e-mail back before the receipient opens it?

[Ty]

If it is sent to someone via the internet - you can't.

If you are on an exchange server then go into sent items
double click on the message and then in the message click
on actions, recall this message. This does NOT always
work - it depends if they open the message before you do
this, etc. So do NOT rely on this method of "undoing" a
sent message.

Ty