The web version of Outlook.com has a useful feature of undoing sent emails. This feature is disabled by default but can be turned on.
Login to Outlook.com
Click on the gear icon from the top right and select View all Outlook settings.
Next, choose Mail > Compose and reply.
Scroll down to Undo send section and drag the slider to right.
The maximum interval up to which the emails can be unsent is 10 seconds.
Click Save for these changes to take place.
Now whenever emails are sent using Outlook.com, a pop-up at the bottom left of the screen will be visible prompting to undo the sent email. This prompt will be visible for the time interval selected from the Undo send section after which the email will be sent.
When the Undo button is clicked, the email message will be restored to its draft form.
Also, there is another useful feature which though is already enabled by default. It’s about reminder for missing attachments.
The settings for it can be changed from Mail > Attachments and disabling the option of Warn me when I send a message that may be missing an attachment.
By default, email messages which are supposed to have attachments but don’t will be held off and you’d get a reminder to add the attachments if any.