You can choose which actions will appear at the top corner of your message when you select a message to read, as well as those that will appear on the message toolbar when you’re composing a message. You can add many actions, or just a few.
Some actions are selected by default, but you can clear them if you prefer.
Choose your version for instructions
The instructions are slightly different depending on whether you're using the new Outlook.com or the classic version. Choose the version you're using to see the instructions that apply to you.
Instructions for the new Outlook.com
To customize actions, do the following:
At the top of the page, select Settings > View all Outlook settings.
Select Mail > Customize actions.
To choose which actions appear at the top corner of your message when you read or reply to email, do the following:
Select the check boxes for the actions you want. They’ll appear at the top corner as you select them.
To change the order in which they appear, select them in a different order.
Instructions for classic Outlook.com
Customizing actions isn't available in classic Outlook.com.