To switch the "From" email address in Outlook without opening a new message window, you can follow these steps:
- Click on the "Options" tab in the ribbon at the top of the Outlook window.
- Click on the "Show From" button in the "Show Fields" section.
- A "From" field will appear above the "To" field in the message window. Click on the "From" field.
- Select the email address you want to use from the drop-down list.
The "From" email address will now be changed in the email you are working on.