If you have access to different inboxes within Outlook, you can send from those emails rather than your personal email address.

Send from a different address in new Outlook

1. Select New mail to start a message.
2. Select the Options tab at the top of the message.
3. Select Show From. A From field appears at the top of your message.

4. Open the From drop-down. If the address you want is listed, select it. If it isn't, select Other email address….

5. Enter the full email address and hit Enter. The address is saved to your From drop-down for future messages. You must have access to that mailbox already to send from.
6. Add your recipients, subject and message, then select Send.

Send from a different address in classic Outlook

1. Select New Email.
2. On the Options tab, select From.

3. Open the From drop-down and choose the address. If it isn't listed, select Other Email Address…, enter it and hit Enter.

4. Finish your message and select Send.

Does this work in Outlook on the web?

Yes. The steps are similar: start a new message, then turn on the From field from the message options and choose your address.