How to choose a different e-mail address to send “from” in Outlook.
Be sure to be granted the permission to send as another user by having your supervisor submit the necessary helpdesk request.
1. Open Outlook and click New Email.
2. On the Options tab of the new email, click From in the Show Fields section to toggle the From field on.

3. On the From drop down menu, select “Other E-mail Address…” and type in the e-mail address you wish to send an e-mail from. Hit OK.
4. The other e-mail address now appears next to From on your Untitled Message window. Compose and send your message as usual.
5. On successive messages, that address will simply appear in the drop down menu for you to pick, so you need not type it every time.