Outlook.com users can never forget to send any attachments while sending email. They can use the “Forgotten attachment reminders” to remind them about the missing attachments. For example, you are trying to send the following message but without any attachment.
Now Outlook.com will check for the missing attachment and display the following message.
Step 1: Click the Settings icon and select More mail settings from the drop down list.
Step 2: In the Outlook Options screen, navigate to Writing email section and click Attachments.
Step 3: Now make sure to mark the radio option with caption as “Check messages for forgotten attachments before sending” and click Save button.