multiple email accounts

I have a primary account in my name plus 2 additional ones for specific department business.   All the mail shows my primary address as the return (& "reply") address.  How do I get each account to "return/reply" to the corresponding address.  Incoming mail goes to the appropriate Inboxes initially.

I have changed the account name from year to year, so the account name shows up but return mail still comes to my main account.