If you’re sending an email on behalf of someone else, you might want people to reply to that person instead of you. Microsoft Outlook gives you the option to choose a different default Reply address to cover this situation.
Once you’ve created your mail, switch to the “Options” tab and then click the “Direct Replies To” button. (Depending on your version of Outlook, you might need to click File > Properties instead.)
Once the Properties window opens, change the address in the “Have replies sent to” box from your address to the address (or addresses, if there is more than one) to which you want replies sent.
Click the “Close” button and then send the mail as usual.
When the recipient receives the mail and clicks “Reply” or “Reply All,” Outlook will automatically fill in the address you’ve chosen. This won’t stop them changing it back to your address (or anyone else’s)—just like a normal email—but it will make it obvious tp whom they are supposed to reply.