how to change signature in outlook? To change your signature in Outlook, open the app and go to "File" > "Options" > "Mail" > "Signatures." Select the signature you want to edit or click "New" to create a new one. Customize your signature with text, images, or links. Once done, click "OK" to save. You can also set different signatures for new emails and replies. This ensures a professional and consistent look in all your communications.