On the Home tab, select New Email.
Click the box and select Other E-mail Address... from the dropdown.
Note: The From field is hidden by default. If the From field is hidden, select Options from within the message you are composing, then select From.
Within the Send From Other E-Mail Addresses window, click From.
Type the email address of the person you want to send as or send on behalf of and click Go.
Then, select the name of the person you want to send as or send on behalf of, and click OK.
Back on the Send From Other E-mail Address window, click OK.
Compose a message as usual and send when ready. Depending on access, the recipient will see one of the following:
- Send as permissions: Your message will appear to have come from the user that granted you this permission.
- Send on behalf of permissions: The "From" address in any message sent by you will indicate that the message was sent by you on behalf of the user that granted you this permission.
If you do not have permission to send from this account, you will receive an email saying Your message did not reach some or all of the intended recipients, followed by the subject, date and time the message was sent and a list of recipients. If you believe you should have permissions to someone's mailbox, you should contact them for verification or ask them to grant you permissions.