This one is typically a longshot, but if you catch it early enough and run into a fair bit of luck, you can often stop email errors before the other party sees them. Essentially, it all boils down to luck and timing. The faster you are at spotting the mistake, and requesting to recall (aka unsend) the email, the better it works.
Unfortunately, the recall function usually only works if it’s going to another Outlook user. Here's how to recall a mistakenly-sent email.
1. Double-click the message you intend to recall.
2. Click "Actions" and select "Recall this message" from the drop-down.
3. Decide whether to delete the message outright, or replace it with a corrected version.
4. Check the box to receive confirmation if it worked, and press OK.
Hopefully, your message is recalled before anyone reads it.