It's simple to open a received message to edit or change the format of messages.
- Open the message.
- On the opened message’s ribbon or menus:
In Outlook 2010: Go to Actions, Edit Message (Actions is in the Move section of the ribbon)
In Outlook 2007: Click on Other Actions, Edit message
In Outlook 2003 and older: Go to the Edit menu, Edit message.
- Edit the message and Save it to save the changes. Close and cancel to discard the changes.
To change the message format (HTML to plain text), look on the Options tab.
How to Convert a Message to Plain Text Format Video Tutorial
Changes are not saved until you Save the message. You can reply or forward the edited message without saving it. (Change the format before hitting Reply to use quote prefix for that format.)