If you have been given permission to send email from a different email account, these instructions show you how to do within Outlook.
1. Click New Email as normal to open a new mail window
2. Click Options, then the From button
3. This will display the From field about the To: box. Click the From drop-down and select Other E-mail Address...
4. A pop-up window appears. Enter the full email address of the account you wish to send from and click OK
5. This email will now send from this email address. The next time you send a new email, it will go back to sending from your default (your own) email address.
You can select on an email-by-email basis which account messages are sent from by simply clicking on the From field and selecting the email account - it will remember any you have added previously.